Different layout in Internet and Firefox

Hi!

I have a website and the layout is not the same in IE and Firefox.
The result in Firefox is what I want, but in IE it's totally different.

There are 4 DIVs and this is the CSS:

.left1{
   float: left;
   clear: left;
   width: 670px;
   height: auto;
}

.left2{
   float: left;
   clear: left;
   width: 670px;
   height: auto;
   margin-top: 15px;
}

.right{
   float: right;
   clear: right;
   width: 300px;
   height: auto;
}

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