LOL you're funny

This is possible, but why? Your banner is very tall so if the side columns got fixed, you couldn't scroll them at all.

DO NOT ADD IT TO YOUR CUSTOM STYLESHEET - it will effect your entire site.

So I tried this with your Enlist page... just add this somewhere on that page. I set the top of the side images to be at 180 pixels from the top. They do overlap the tab bar and banner, but you can see it works.

#ctl00_ContentPlaceHolder1_ContentPane {position:absolute; width:45%; left: 360px; }
#ctl00_ContentPlaceHolder1_LeftPane { position:fixed; left:0px; top:180px;}
#ctl00_ContentPlaceHolder1_RightPane { position:fixed; right:0px; top:180px; }

The middle column is set to 45% of the browser width, but it might be more ideal to fix the width to maintain the appearance no matter the browser width. You can also see the left image is overlapped by the center and the right image overlaps the center - this is just the order that the columns are in the HTML, something you can't really change because GP sets up the columns in that order.

I messed around with your Home page too. It only needed slight modification of the CSS above. Once again it covers up your banner and tab bar.

#ctl00_ContentPlaceHolder1_ContentPane {position:absolute; width:65%; left: 210px; }
#ctl00_ContentPlaceHolder1_LeftPane { position:fixed; left:0px; top:50px;}
#ctl00_ContentPlaceHolder1_RightPane { position:fixed; right:0px; top:50px; }

I don't think this was exactly what you wanted, but maybe show me which page you want to do this do, and what you want to do with the banner and tab bar and I can look into it

:)

Hmmm, ok how about this...

The side boxes are fixed in place and now have scroll bars (I tried this on your home page). I added CSS to hide your banner (since it's HUGE), because it fixes the side boxes very close to the bottom of the page... I only did this so you can see what this CSS does.

.BannerArea {display:none}
#ctl00_ContentPlaceHolder1_ContentPane { width:60%; }
#ctl00_ContentPlaceHolder1_LeftPane { position:fixed; height:80%; overflow:auto; }
#ctl00_ContentPlaceHolder1_RightPane { position:fixed; height:80%; overflow:auto; }

Try just saving the main page source to your desktop, then add this into the CSS area.