Help wtih adding margins [CSS]

Hi, I'm fairly new to CSS and I'm working with a template to try to modify the layout. Anyways, my problem is with adding the margin-top property to a class for a table within a div id. Basically, I have a div tag which has a background applied to it and within the div I have a bunch of tables and a margin-top 30px property applied to each table that is needed to add some space in between the tables. This works fine but the problem is the background image (in the div tag) does not stay at the top in some browsers (such as IE or Chrome) but works fine in Firefox. The background image in some browsers is moved to the start of the top the first table.

An example of what I mean is here: http://alturl.com/b75g Notice on the right side (in Firefox) the black shadowy bar at the top is aligned perfectly to the top white/greyish menu bar but in IE or Chrome the black shadowy bar is slightly lowered and is placed at the top of the first table (which has a margin-top of 30px).

Can anyone help me out in what the problem may be? I can post the CSS here or if someone can analyze it with Firebug that would be great! Thanks.