what happens when i declare a doctype? from what I've understood, when i load a page with a doctype declaration it downloads a DTD page which includes a set of rules that tells my browser how to display that page. but isn't it something the browser does? that's why i see different results in firefox and IE for example. and what happens when i declare nothing?
That was the idea but browsers don't do this for HTML. The browser already has these 'rules' built in and only checks to see if a doctype is declared. The rules are followed better by some browsers. IE is the worst of the bunch. Every other browser is far more advanced. You are dumped into 'quirks mode' which is like time traveling to the 1990s. You don't want to be there.