There is the semicolon missing (;) after the "50%"
but you should also notice that the percentage of your div is connected to the div that contains it.
for instance:
<div id="wrapper">
<div class="container">
adsf
</div>
</div>
#wrapper {
height:100px;
}
.container
{
width:80%;
height:50%;
background-color:#eee;
}
here the height of your .container will be 50px. it will be 50% of the 100px from the wrapper div.
if you have:
adsf
#wrapper {
height:400px;
}
.container
{
width:80%;
height:50%;
background-color:#eee;
}
then you .container will be 200px. 50% of the wrapper.
So you may want to look at the divs "wrapping" your ".container"...