The problem is not a really a css or an html problem but a problem with the sizes you picked.

.navleft { width:100px; float:left; display:block; height:50px; overflow:hidden; }
.navright { width:150px; float:right; display:block; height:50px; overflow:hidden; }
.contentleft { top:0; margin:0; width:500px; float:left; display:block; background:#FFF; color: #000; overflow: hidden; height:100px; }
.contentright { top:0; left:0; margin:0; width:141px; float:right; display:block; color:#FFF; overflow:hidden; height:400px; }

change that to

.navleft { width:500px; float:left; display:block; height:50px; overflow:hidden; }
.navright { width:150px; float:right; display:block; height:50px; overflow:hidden; }
.contentleft { top:0; margin:0; width:500px; float:left; display:block; background:#FFF; color: #000; overflow: hidden; height:500px; }
.contentright { top:0; left:0; margin:0; width:150px; float:right; display:block; color:#FFF; overflow:hidden; height:400px; }

that should clean it up. You basically just had your wrapper to large and your contents to small.

__________________
iSearchNotes.com - Share College Student Notes | Blog