Testing different PC screens / resolutions

I have uploaded the PS3, and edited the template to have 6 page headings across the top.

It works fine with my "normal" work-type 17in screen (13.25"w x 10.50"h, resolution range from 1025x768 upto 1280x1024), but on a wide-screen 18.5" display screen (16"w x 9"h, resolution 1366x768 - where 768 is my max ht) the horizontal menu does not display correctly.

What happens is that the horizontal item including search is fine. But the horizontal menu is only visible, very faintly, at the very top of the menu items. When I use the mouse to hover over the links they appear, but only whilst I hover.

If I click on any link except home, my content disappears to the far right.

By editing the css, eg to a much smaller font-size, I have made it work (I have changed menu.css to make the font-size smaller throughout, the link width (in cssmw_home > li > span > a) to 90px and the margin to 2px 0 0 0.). But logically, how many "page links" do you think it is reasonable to add to the top navigation bar?

Thanks, Nick