HTML中DOCTYPE的定义及用法(1) The <!DOCTYPE> declaration is the very first thing in your document, before the <html> tag. This tag tells the browser which HTML or XHTML specification the document uses.
Note: The <!DOCTYPE> tag does not have an end tag!
HTML HTML 4.01 specifies three document types: Strict, Transitional, and Frameset.
HTML Strict DTD
Use this when you want clean markup, free of presentational clutter. Use this together with Cascading Style Sheets (CSS技巧">CSS):
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
HTML Transitional DTD
The Transitional DTD includes presentation attributes and elements that W3C eXPects to move to a style sheet. Use this when you need to use HTML's presentational features because your readers don't have browsers that support Cascading Style Sheets (CSS):
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
