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">