When I look at my personal site, it looks perfectly fine. However, Google's and Bing's caches show an ugly gap above the footer. Do you see a gap above the footer? http://www.thomasmottl.com/ Also, is the layout acceptable?
Your use of an incomplete reset and/or failing to set how UL/OL/P handle padding/margins is likely the culprit, some browsers use margin-bottom, some padding-bottom, and not all handle margin-collapse the same. Though honestly I think you need more gaps in terms of padding between LI and around the outer edge to make it clearer they are separate items (since you killed their bullets), and I'm not sure I'd make that second set (the OL) a list in the first place. If it is, I'd put the numbering back in there! Also not sure I'd make those H3, since they don't seem to actually be subsections of the "welcome" text in the h2. If I were to complain about 'gaps' it would be for the menu and heading alignment at the top (flush bottom and flush top next to each-other looks like a rendering error) and the LACK of a gap after the footer. Also the lack of min-width makes the page really hard to follow at higher resolutions.