Hello chriggi,
First of all lemme say thank you for enjoying my tutorial

Secondly I do believe I've come up witha quick-fix for this situation:
#1 Save
this image as barbg.png and upload it to your images/ folder.
That image is a background-image and will be used to make it look like all 3 of your content boxes.
#2: Save
this image as bottom.png and upload it to your images/ folder.
That image is the bottom borders of all 3 of your content boxes.
Now then now that you have your images uploaded to your server. Delete all 3 images from your source-code, the images that are in the nav_btm, content_btm, and news_btm divs. (Because we no longer need these bottom borders as we're about to use new ones.) Now, add <img src="images/bottom.png" width="702" height="1" alt="Bottom Borders" /> in your footer div. Just before your copyright image. This will add the bottom borders for your content boxes to your page.
Save and upload your new index.html
Now heres your new CSS I've made a few changes to such as adding the new background-image to your container div, and adding defninitions to your footer div. Telling it to clear: both, and giving it a width, and height attribute:
body{
background-image: url(images/bg.jpg) !important;
background-repeat: repeat;
text-align: center; /*centers our layout in some browsers*/
}
#container{
width: 702px; /*The width of our layout*/
height: auto;
background-image: url(images/barbg.png) !important;
background-repeat: repeat-y;
margin-left: auto;
margin-right: auto;
/*Margin left and right set to auto center's our layout*/
text-align: left; /*Resets the text alignment*/
}
#banner{
width: 702px;
height: 166px;
}
#left{
width: 195px;
float: left;
}
#nav_mid{
background-image: url(images/index_10.jpg) !important;
background-repeat: repeat-y
font-family: Verdana, arial, sans-serif;
font-size: 12px;
color: #000000;
padding: 10px;
}
#center{
width: 311px;
float: left;
}
#content_mid{
background-image: url(images/index_11.jpg) !important;
background-repeat: repeat-y
font-family: Verdana, arial, sans-serif;
font-size: 12px;
color: #000000;
padding: 10px;
}
#right{
width: 196px;
float: right;
}
#news_mid{
background-image: url(images/index_12.jpg) !important;
background-repeat: repeat-y
font-family: Verdana, arial, sans-serif;
font-size: 12px;
color: #000000;
padding: 10px;
}
#footer{
width: 702px;
height: 19px;
clear: both;
}
Note: that the clear: both in your footer should fix your IE problem as well.
Tested In: Firefox, Opera, IE7, Netscape and Flock
Now then I hope that was understandable. If you have any further questions please feel free to ask. Good luck