HTML document types
There are three document type definitions in HTML. Each document type definition specifies what type of document an HTML document will be.
This lesson focuses on:
- Specifying a document type definition
- The Transitional document type definition
- The Frameset document type definition
- The Strict document type definition
Specifying a document type definition
A document type definition is specified with the <!DOCTYPE> declaration. The <!DOCTYPE> declaration should be the first line of code in an HTML document, even before the <html> tag.
NOTE: The <!DOCTYPE> declaration is mandatory and should always be the first thing in an HTML document.
NOTE: Although a document type definition is technically not required for a functioning webpage, it is good practice to always include it in your webpages. As you learn to build webpages, get into the habit of always including the document type definition in your code.
Example:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <title>Specifying a document type</title> </head> <body> </body> </html>
The line of code that specifies the document type definition is:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
The rest of the HTML document:
<html> <head> <title>Specifying a document type</title> </head> <body> </body> </html>
The Transitional document type definition
The Transitional document type definition specifies an HTML document that uses some deprecated features such as the <font> tag, and can also be used for documents that will be displayed in browsers that do not support Cascading Style Sheets.
Example:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <title>Specifying a document type</title> </head> <body> </body> </html>
The Frameset document type definition
The Frameset document type definition specifies an HTML document that uses frames to display one or more pages at the same time in the browser window. The Frameset document type definition is similar to the Transitional document type definition, but unlike the Transitional document type definition, the Frameset document type definition uses the <frameset> tag instead of the <body> tag.
Example:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN" "http://www.w3.org/TR/html4/frameset.dtd"> <html> <head> <title>Specifying a document type</title> </head> <frameset cols="50%, 50%"> <frame src="frame1.php" /> <frame src="frame2.php" /> </frameset> </html>
The Strict document type definition
The Strict document type definition specifies an HTML document that contains really clean markup with no presentational clutter, and does not use any deprecated features such as the <font> tag. The strict document type should be used together with Cascading Style Sheets.
Example:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title>Specifying a document type</title>
</head>
<body>
<h1>Content</h1>
</body>
</html>
Examples
Transitional document
This example demonstrates creating a transitional HTML document.
Frameset
This example demonstrates creating a frameset HTML document.
