Try This.
CSS
.container{
position: relative;
min-height: 100%;
}
.leftDiv{
float: left;
min-height: 100%;
background: #f0f0f0;
width: 10%;
}
.rightDiv{
float: left;
background: blue;
color: white;
width:90%;
height: 100%;
}
HTML
<div class="container">
<div class="leftDiv">
<p>This is the left div</p>
</div>
<div class="rightDiv">
<p>This is the Right Div</p>
</div>
Can't understand your coding. The best interpretation I could come up is that you want 2 divs lie next to each other, so I made a parent div .container here, position it to relative so that all its children divs will rely on it for positioning and dimensions, I also give it min height of 100% for demo purposes.
Then the divs that lie next to each other are the .leftDiv and the .rightDiv, each floated left so that the element next to it will take the remaining space of the parent it didn't cover. Also I gave it widths 10% and 90%, and a height of 100% again for demo purposes.