DHTML ONLINE » HTML Advance http://dhtmlonline.com HTML and DHTML tutorials Tue, 15 Sep 2009 09:37:55 +0000 http://wordpress.org/?v=2.8.4 en hourly 1 HTML Layout http://dhtmlonline.com/html-layout/ http://dhtmlonline.com/html-layout/#comments Tue, 15 Sep 2009 09:14:29 +0000 admin http://dhtmlonline.com/?p=56 Everywhere on the Web you will find pages that are formatted like newspaper pages using HTML columns.

HTML Layout – Using Tables

One very common practice with HTML, is to use HTML tables to format the layout of an HTML page.A part of this page is formatted with two columns, like a newspaper page.

As you can see on this page, there is a left column and a right column.

This text is displayed in the left column.

 An HTML <table> is used to divide a part of this Web page into two columns.The trick is to use a table without borders, and maybe a little extra cell-padding.

No matter how much text you add to this page, it will stay inside its column borders.

Same Layout – Color Added

One very common practice with HTML, is to use HTML tables to format the layout of an HTML page.A part of this page is formatted with two columns, like a newspaper page.

As you can see at this page, there is a left column and a right column.

 An HTML <table> is used to divide a part of this Web page into two columns.This text is displayed in the right column.

The trick is to use a table without borders, and maybe a little extra cell-padding.

No matter how much text you add to this page, it will stay inside its column borders.
]]> http://dhtmlonline.com/html-layout/feed/ 0 HTML Fonts http://dhtmlonline.com/html-fonts/ http://dhtmlonline.com/html-fonts/#comments Tue, 15 Sep 2009 09:13:55 +0000 admin http://dhtmlonline.com/html-fonts/ The <font> tag in HTML is deprecated. It is supposed to be removed in a future version of HTML.

Even if a lot of people are using it, you should try to avoid it, and use styles instead.

The HTML <font> Tag

With HTML code like this, you can specify both the size and the type of the browser output :

<p>
<font size="2" face="Verdana">
This is a paragraph.
</font>
</p>
<p>
<font size="3" face="Times">
This is another paragraph.
</font>
</p>

Font Attributes

Attribute Example Purpose
size=”number” size=”2″ Defines the font size
size=”+number” size=”+1″ Increases the font size
size=”-number” size=”-1″ Decreases the font size
face=”face-name” face=”Times” Defines the font-name
color=”color-value” color=”#eeff00″ Defines the font color
color=”color-name” color=”red” Defines the font color

The <font> Tag Should NOT be Used

The <font> tag is deprecated in the latest versions of HTML (HTML 4 and XHTML).

The World Wide Web Consortium (W3C) has removed the <font> tag from its recommendations. In future versions of HTML, style sheets (CSS) will be used to define the layout and display properties of HTML elements.

]]> http://dhtmlonline.com/html-fonts/feed/ 0 HTML 4.0 Why http://dhtmlonline.com/html-4-0-why/ http://dhtmlonline.com/html-4-0-why/#comments Tue, 15 Sep 2009 09:13:27 +0000 admin http://dhtmlonline.com/html-4-0-why/ HTML 3.2 Was Very Wrong !

The original HTML was never intended to contain tags for formatting a document. HTML tags were intended to define the content of the document like:

<p>This is a paragraph</p>

<h1>This is a heading</h1>

When tags like <font> and color attributes were added to the HTML 3.2 specification, it started a nightmare for web developers. Development of large web sites where fonts and color information had to be added to every single Web page, became a long, expensive and unduly painful process.

What is so Great About HTML 4.0 ?

In HTML 4.0 all formatting can be removed from the HTML document and stored in a separate style sheet.

Because HTML 4.0 separates the presentation from the document structure, we have what we always needed: Total control of presentation layout without messing up the document content.

What Should You do About it ?

Do not use presentation attributes inside your HTML tags if you can avoid it. Start using styles!

Do not use deprecated tags.

Prepare Yourself for XHTML

XHTML is the “new” HTML. The most important thing you can do is to start writing valid HTML 4.01. Also start writing your tags in lower case. Always close your tag elements. Never end a paragraph without </p>.

NOTE: The official HTML 4.01 recommends the use of lower case tags.

Validate Your HTML Files as HTML 4.01

An HTML document is validated against a Document Type Definition (DTD). Before an HTML file can be properly validated, a correct DTD must be added as the first line of the file.

The HTML 4.01 Strict DTD includes elements and attributes that have not been deprecated or do not appear in framesets:

<!DOCTYPE HTML PUBLIC
"-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">

The HTML 4.01 Transitional DTD includes everything in the strict DTD plus deprecated elements and attributes:

<!DOCTYPE HTML PUBLIC
"-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">

The HTML 4.01 Frameset DTD includes everything in the transitional DTD plus frames as well:

<!DOCTYPE HTML PUBLIC
"-//W3C//DTD HTML 4.01 Frameset//EN"
"http://www.w3.org/TR/html4/frameset.dtd">
]]> http://dhtmlonline.com/html-4-0-why/feed/ 0 HTML Styles http://dhtmlonline.com/html-styles/ http://dhtmlonline.com/html-styles/#comments Tue, 15 Sep 2009 09:12:54 +0000 admin http://dhtmlonline.com/?p=52 With HTML 4.0 all formatting can be moved out of the HTML document and into a separate style sheet.

How to Use Styles

When a browser reads a style sheet, it will format the document according to it. There are three ways of inserting a style sheet:

External Style Sheet

An external style sheet is ideal when the style is applied to many pages. With an external style sheet, you can change the look of an entire Web site by changing one file. Each page must link to the style sheet using the <link> tag. The <link> tag goes inside the head section.

<head>
<link rel="stylesheet" type="text/css"
href="mystyle.css">
</head>

Internal Style Sheet

An internal style sheet should be used when a single document has a unique style. You define internal styles in the head section with the <style> tag.

<head>
<style type="text/css">
body {background-color: red}
p {margin-left: 20px}
</style>
</head>

Inline Styles

An inline style should be used when a unique style is to be applied to a single occurrence of an element.

To use inline styles you use the style attribute in the relevant tag. The style attribute can contain any CSS property. The example shows how to change the color and the left margin of a paragraph:

<p style="color: red; margin-left: 20px">
This is a paragraph
</p>

Style Tags

Tag Description
<style> Defines a style definition
<link> Defines a resource reference
<div> Defines a section in a document
<span> Defines a section in a document
<font> Deprecated. Use styles instead
<basefont> Deprecated. Use styles instead
<center> Deprecated. Use styles instead
]]> http://dhtmlonline.com/html-styles/feed/ 0 HTML Head http://dhtmlonline.com/html-head/ http://dhtmlonline.com/html-head/#comments Tue, 15 Sep 2009 09:12:15 +0000 admin http://dhtmlonline.com/?p=50 The Head Element

The head element contains general information, also called meta-information, about a document. Meta means “information about”.

You can say that meta-data means information about data, or meta-information means information about information.

Information Inside the Head Element

The elements inside the head element should not be displayed by a browser.

According to the HTML standard, only a few tags are legal inside the head section. These are: <base>, <link>, <meta>, <title>, <style>, and <script>.

Look at the following illegal construct:

<head>
  <p>This is some text</p>
</head>

In this case the browser has two options:

  • Display the text because it is inside a paragraph element
  • Hide the text because it is inside a head element

If you put an HTML element like <h1> or <p> inside a head element like this, most browsers will display it, even if it is illegal.

Should browsers forgive you for errors like this? We don’t think so. Others do.

Head Tags

Tag Description
<head> Defines information about the document
<title> Defines the document title
<base> Defines a base URL for all the links on a page
<link> Defines a resource reference
<meta> Defines meta information
Tag Description
<!DOCTYPE> Defines the document type. This tag goes before the <html> start tag.
]]> http://dhtmlonline.com/html-head/feed/ 0 HTML Meta http://dhtmlonline.com/html-meta/ http://dhtmlonline.com/html-meta/#comments Tue, 15 Sep 2009 09:11:43 +0000 admin http://dhtmlonline.com/html-meta/ The Meta Element

As we explained in the previous chapter, the head element contains general information (meta-information) about a document.

HTML also includes a meta element that goes inside the head element. The purpose of the meta element is to provide meta-information about the document.

Most often the meta element is used to provide information that is relevant to browsers or search engines like describing the content of your document.

Note: W3C states that “Some user agents support the use of META to refresh the current page after a specified number of seconds, with the option of replacing it by a different URI. Authors should not use this technique to forward users to different pages, as this makes the page inaccessible to some users. Instead, automatic page forwarding should be done using server-side redirects” at http://www.w3.org/TR/html4/struct/global.html#adef-http-equiv.

Keywords for Search Engines

Some search engines on the WWW will use the name and content attributes of the meta tag to index your pages.

This meta element defines a description of your page: <meta name=”description” content=”Free Web tutorials on HTML, CSS, XML, and XHTML”>
This meta element defines keywords for your page:<meta name=”keywords” content=”HTML, DHTML, CSS, XML, XHTML, JavaScript, VBScript”>

The intention of the name and content attributes is to describe the content of a page.

However, since too many webmasters have used meta tags for spamming, like repeating keywords to give pages a higher ranking, some search engines have stopped using them entirely.

Unknown Meta Attributes

Sometimes you will see meta attributes that are unknown to you like this:

<meta name=”security” content=”low”>

Then you just have to accept that this is something unique to the site or to the author of the site, and that it has probably no relevance to you.

]]> http://dhtmlonline.com/html-meta/feed/ 0 HTML URLs http://dhtmlonline.com/html-urls/ http://dhtmlonline.com/html-urls/#comments Tue, 15 Sep 2009 09:11:08 +0000 admin http://dhtmlonline.com/html-urls/ HTML Links

When you click on a link in an HTML document like this: Last Page, an underlying <a> tag points to a place (an address) on the Web with an href attribute value like this: <a href=”index.asp”>Last Page</a>.

The Last Page link in the example is a link that is relative to the Web site that you are browsing, and your browser will construct a full Web address like http://www.codedcode.com/html/index.asp to access the page.

Uniform Resource Locators

Something called a Uniform Resource Locator (URL) is used to address a document (or other data) on the World Wide Web. A full Web address like this: http://www.codedcode.com/html/index.asp follows these syntax rules:

scheme://host.domain:port/path/filename

The scheme is defining the type of Internet service. The most common type is http.

The domain is defining the Internet domain name like codedcode.com.

The host is defining the domain host. If omitted, the default host for http is www.

The :port is defining the port number at the host. The port number is normally omitted. The default port number for http is 80.

The path is defining a path (a sub directory) at the server. If the path is omitted, the resource (the document) must be located at the root directory of the Web site.

The filename is defining the name of a document. The default filename might be default.asp, or index.html or something else depending on the settings of the Web server.

URL Schemes

Some examples of the most common schemes can be found below:

Schemes Access
file a file on your local PC
ftp a file on an FTP server
http a file on a World Wide Web Server
gopher a file on a Gopher server
news a Usenet newsgroup
telnet a Telnet connection
WAIS a file on a WAIS server

Accessing a Newsgroup

The following HTML code:

<a href=”news:alt.html”>HTML Newsgroup</a>

creates a link to a newsgroup like this HTML Newsgroup.

Downloading with FTP

The following HTML code:

<a href=”ftp://www.codedcode.com/ftp/winzip.exe”>Download WinZip</a>

creates a link to download a file like this: Download WinZip.

(The link doesn’t work. Don’t try it. It is just an example. codedcode doesn’t really have an ftp directory.)

Link to your Mail system

The following HTML code:

<a href=”mailto:someone@codedcode.com”>someone@codedcode.com</a>

creates a link to your own mail system like this:

someone@codedcode.com

]]> http://dhtmlonline.com/html-urls/feed/ 0 HTML Scripts http://dhtmlonline.com/html-scripts/ http://dhtmlonline.com/html-scripts/#comments Tue, 15 Sep 2009 09:10:05 +0000 admin http://dhtmlonline.com/?p=46 Add scripts to HTML pages to make them more dynamic and interactive.

Insert a Script into HTML Page

A script in HTML is defined with the <script> tag. Note that you will have to use the type attribute to specify the scripting language.

<html>
<head>
</head>
<body>
<script type="text/javascript">
document.write("Hello World!")
</script>
</body>
</html>

The script above will produce this output:

Hello World!

How to Handle Older Browsers

A browser that does not recognize the <script> tag at all, will display the <script> tag’s content as text on the page. To prevent the browser from doing this, you should hide the script in comment tags. An old browser (that does not recognize the <script> tag) will ignore the comment and it will not write the tag’s content on the page, while a new browser will understand that the script should be executed, even if it is surrounded by comment tags.

Example

JavaScript:
<script type=”text/javascript”>
<!–
document.write(”Hello World!”)
//–>
</script>VBScript:
<script type=”text/vbscript”>
<!–
document.write(”Hello World!”)
‘–>
</script>

The <noscript> Tag

In addition to hiding the script inside a comment, you can also add a <noscript> tag.

The <noscript> tag is used to define an alternate text if a script is NOT executed. This tag is used for browsers that recognize the <script> tag, but do not support the script inside, so these browsers will display the text inside the <noscript> tag instead. However, if a browser supports the script inside the <script> tag it will ignore the <noscript> tag.

Example

JavaScript:
<script type=”text/javascript”>
<!–
document.write(”Hello World!”)
//–>
</script>
<noscript>Your browser does not support JavaScript!</noscript>VBScript:
<script type=”text/vbscript”>
<!–
document.write(”Hello World!”)
‘–>
</script>
<noscript>Your browser does not support VBScript!</noscript>

Script Tags

Tag Description
<script> Defines a script
<noscript> Defines an alternate text if the script is not executed
<object> Defines an embedded object
<param> Defines run-time settings (parameters) for an object
<applet> Deprecated. Use <object> instead
]]> http://dhtmlonline.com/html-scripts/feed/ 0 HTML Attributes http://dhtmlonline.com/html-attributes/ http://dhtmlonline.com/html-attributes/#comments Tue, 15 Sep 2009 09:09:31 +0000 admin http://dhtmlonline.com/?p=44 HTML tags can have attributes. The special attributes for each tag are listed under each tag description. The attributes listed here are the core and language attributes that are standard for all tags (with a few exceptions):

Core Attributes

Not valid in base, head, html, meta, param, script, style, and title elements.

Attribute Value Description
class class_rule or style_rule The class of the element
id id_name A unique id for the element
style style_definition An inline style definition
title tooltip_text A text to display in a tool tip

Language Attributes

Not valid in base, br, frame, frameset, hr, iframe, param, and script elements.

Attribute Value Description
dir ltr | rtl Sets the text direction
lang language_code Sets the language code

Keyboard Attributes

Attribute Value Description
accesskey character Sets a keyboard shortcut to access an element
tabindex number Sets the tab order of an element
]]> http://dhtmlonline.com/html-attributes/feed/ 0 HTML Events http://dhtmlonline.com/html-events/ http://dhtmlonline.com/html-events/#comments Tue, 15 Sep 2009 09:08:46 +0000 admin http://dhtmlonline.com/html-events/ New to HTML 4.0 is the ability to let HTML events trigger actions in the browser, like starting a JavaScript when a user clicks on an HTML element. Below is a list of attributes that can be inserted into HTML tags to define event actions.

Window Events

Only valid in body and frameset elements.

Attribute Value Description
onload script Script to be run when a document loads
onunload script Script to be run when a document unloads

Form Element Events

Only valid in form elements.

Attribute Value Description
onchange script Script to be run when the element changes
onsubmit script Script to be run when the form is submitted
onreset script Script to be run when the form is reset
onselect script Script to be run when the element is selected
onblur script Script to be run when the element loses focus
onfocus script Script to be run when the element gets focus

Keyboard Events

Not valid in base, bdo, br, frame, frameset, head, html, iframe, meta, param, script, style, and title elements.

Attribute Value Description
onkeydown script What to do when key is pressed
onkeypress script What to do when key is pressed and released
onkeyup script What to do when key is released

Mouse Events

Not valid in base, bdo, br, frame, frameset, head, html, iframe, meta, param, script, style, title elements.

Attribute Value Description
onclick script What to do on a mouse click
ondblclick script What to do on a mouse double-click
onmousedown script What to do when mouse button is pressed
onmousemove script What to do when mouse pointer moves
onmouseout script What to do when mouse pointer moves out of an element
onmouseover script What to do when mouse pointer moves over an element
onmouseup script What to do when mouse button is released
]]> http://dhtmlonline.com/html-events/feed/ 0