Q:

What is the point in the doctype declaration at the top of html form? Does it change anything?

Been writing web apps for years and this line:
<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Transitional//EN\" \"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

Has always confused me. What is it for exactly? What are the implications if I remove it?
I understand the w3c conventions about nested elements etc but what actually happens why is the declaration there do browsers fail or something if I take it out?
Cheers,
Pete

A:

It kicks the browser into standards mode, which makes the browser properly render elements. Not every doctype kicks the browser into standards mode, see this chart. If a valid doctype is not used to kick the browser into standards mode, the browser will basically try to render your page according to "standards" ( or lack thereof ) in 2002-2003 when everyone used crappy table layouts. You do not want quirks mode.
Conclusion: always use a doctype.

