making div's change size as needed

Hi how do you make div's get larger or smaller according to what's in them I have one that contents the body of my work however its to small for one page with a lot of long content on it (a kind of blog) can I make the div get longer as needed
TAR

I dont use div that much. (even though I should)

uhm..
have you tried..

(not sure what auto does..)
test it out on a simple test page to see if it works.

Yes tar the <div style="width:100%"></div> one works and it can be changed to <div style="height:100%"></div> as well tar!