More Crossbrowser Complaints

After the debacle of my last project rendering so unexpectedly,I was curious to see if my other websites looked fine in Linux OS, since I never have access to that kind of machine.
I visited browsershots.org again and loaded a couple of pages from the stonestreetpress.com website.Now I’m even more confused.Because both pages look pretty the same, even in IE 5.5 and I was sure there would be discrepancies.
The home page of ssp.com is kind of complicated and has floated divs and lists and whathaveyou all over it.Yet it renders just fine.
So why does that one simple html form not render 100% accurately in Linux?
Just to show you what I’m talking about here is a group of screenshots in a bunch of browsers
Except where the machine’s screen cuts off the bottom of the page in some of the screenshots-they all look the same.
I’m officially stumped.