CSS <div> Style Shorter than Child Element - html

Question

I'm working on a project to better my knowledge of Spring MVC practices. To do this, I've been creating a very scaled down version of Twitter. Basically, a user can sign in and post a little blurb and also see a timeline of their previous blurbs and all their follower's blurbs.
I have a background image across the whole page and a container in the middle with a light blue background for just the post blurb box and the timeline. The light blue background only goes to the bottom of the visible page. If the timeline goes down past a single page view where you have to scroll down, the light blue background stops at the bottom of what was visible on the initial load.
I have my page defined like this:
The div class=blurb is the blurbs in the timeline.
<div id="container">
<div id="mainPanel">
<div id="timeline">
<div class="class="blurb"">
<span class="user">test</span> <span
class="displayName">Test User</span> <span class="bodytext">This is a small blurb.</span>
<span class="timestamp">1 hours ago</span>
</div>
<div class="blurb">
<span class="user">admin</span> <span
class="displayName">Test admin</span> <span class="bodytext">This is another small blurb.</span>
<span class="timestamp">1 hours ago</span>
</div>
</div>
</div>
</div>
The CSS style for the container is shown below.
#container {
width: 650px;
height: 100%;
margin: 0 auto;
padding: 10px;
background-color: #DDEEF6;
}
Can I modify that container CSS in a way to make it be as long as the timeline is? The timeline grows with every blurb post.
Screenshot with height defined to 100%
Screenshot with height undefined
UPDATE:
Okay, so it absolutely has to do with the floats. Thanks to the two commenters below. The #socialPanel is defined as such:
#socialPanel {
width: 250px;
float: right;
}
Using Chrome's developer tools, if I clear the float is drops the social panel below my blurbs/tweets and moves the light blue background all the way down the list of blurbs.
Any suggestions on what I could research to keep the socialPanel floating left at the top, but still have my light blue background use all the available height? Many thanks on helping me figure it out this far!
UPDATE TWO:
I combined the methods shown in the answer below to solve my problem. I added a div with class clearer with clear:both; and then removed the height: 100%; from the #container styling. This resolved the problem.
NOTE:
Adding the overflow: hidden; to my container's styling made the page cut off after the light blue area, it did not make the light blue area go all the way down.
Many thanks to all the help! I'm still learning and it was all very appreciated!!

Answer 1

Place overflow:hidden on the #container.
How does it work?
One would think placing this style on a container would hide the floats instead of containing them. What actually happens is that overflow:hidden makes the element establish a new block formatting context. This fixes the float containment of any children floating within it. This CSS fix is more practical then including an additional element in the HTML styled with clear:both and works on all modern browsers, including IE7+.

Answer 2

You probably just need to add a clearing div after your two inner divs. http://jsfiddle.net/c3vTU/1/
<div class="outer">
<div class="inner-left"> Stuff on the left</div>
<div class="inner-right">Stuff on the right <br/><br/></div>
<div class="clearer"> </div>
</div>
CSS
.outer {
width: 520px;
padding: 10px;
background-color: #eee;
}
.inner-left {
float: left;
width: 300px;
background-color: red;
}
.inner-right {
float: right;
width: 200px;
background-color: yellow;
}
.clearer {
clear: both;
}
As #MichaelIrigoyen noted, you can also just add overflow: hidden or overflow:auto (I think makes more sense) to your container. http://jsfiddle.net/c3vTU/4/ This is cleaner and I love it!

Answer 3

If you simply remove the height declaration (height: 100%;) from #container, it will expand as its children do (and the background of course, too).