Use of Proper Doctypes
DTD stands for Document Type Definitions and also referred to as a doctype. There are 3 specific doctypes. The specification of a doctype will make all the difference in some browsers especially Internet Explorer.
Strict
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
Transitional
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-loose.dtd">
Frameset
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd">
There are doctypes for those of you who use HTML 4.0 Standards. These doctypes can be found at this site: http://www.alistapart.com/articles/doctype/
What is a Div?
A div is a special type of tag that is a logical division of content. This means that each major section of your layout is contained in a div. You can think of divs as shaped as squares or rectangles depending on the length of content within them.
<div> </div>