two DIV nesting!why they can't evaluate the height automatically

[allan1022]

I have some questions wante to get your help.
In my layout has A,B,C blocks
the height of A changes with it's content
the height of B is fixed
then how can make the height of C change with the height of A automatically
the height of C = the height of A - the height of B
I make C 100% and AUTO all can't work
where is wrong

<div style="width:500px; border:1px solid black;float:inherit;"> 
 <div style="width:200px; border:1px solid black;margin:2px;height:30;float:left"></div>
 <div style="width:270px; border:1px solid black;margin:2px;height:30;float:left"></div>
 <div style="width:270px;border:1px solid black;margin:2px;height:30;float:left">block A<br />
 <br />
 <br />
 <br />
 <br />
 <br />
 <br />
 <br />
 <br />
 <br />
 <br />
 <br />
 <br />
 <br />
 <br />
 <br />
 <br /></div>
 <div style="width:210px; border:1px solid black;margin:2px;height:30;float:left">block B</div>
 <div style="width:210px; border:1px solid black;margin:2px;height:30;float:left">block C</div>
</div> 

[DrDoc]

Welcome to Webmaster World!

The "problem" in your case is the use of floating elements. The W3C specification sheds some extra light on the matter:
[w3.org...]
[w3.org...]