When I view the site in Windows then most of the site, like the top text, right contact details, nav text and welcome text appear lower than they do on the mac. Mac browsers sho
Different browsers have different CSS presets, or defaults. Therefore the default rendering will vary. In order to get around this problem, you can use a CSS reset stylesheet. Here is one that works well:
http://meyerweb.com/eric/tools/css/reset/
Using a reset stylesheet will remove any browser defaults. You can then add in your own margin/padding styling. This may require some adjustments to your current CSS values, but it will help overall when making your CSS cross-browser compatible.