The div height varies with the window, and the div window changes.
<! DOCTYPE html PUBLIC "-// W3C // dtd xhtml 1.0 Transitional // EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<Html xmlns = "http://www.w3.org/1999/xhtml">
<Head>
<Title> CSS layout: The div height varies with the window. </title>
<Style>
* {Margin: 0px ;}
Html {height: 100% ;}
Body {height: 100% ;}
Div {margin: 0 auto ;}
# Top {width: 800px; min-height: 100%; background-color: # 00f ;}
* Html # top {height: 100%; background-color: # f00 ;}
* Html body {height: 100% ;}
# Topz {width: 800px; height: 60px; background: # ddd ;}
# Topx {width: 800px; height: 50px; background: # ccc ;}
</Style>
</Head>
<Body>
<Div id = "top">
The div height varies with the window.
</Div>
<Div id = "topx">
<H2> China's largest Chinese search engine. </H2>
</Div>
<Div> http://www.999jiujiu.com/</div>
</Body>
</Html>