desktop template width firefox vs explorer

Any thoughts on this: when I view my site on explorer it delivers at 1100 pixels width, when viewed on firefox it delivers at 900 pixels (from the same laptop). My settings in the template are for 1000 pixels.

Would love a fix for this. I'm leaning to a standard setting of 1100 in the template settings (determine the exact setting after testing).
Thanks!

url is https://www.golfsgreatheritage.com

For the template has 1000px on IE8 (look here http://d.pr/i/iT4Z) and the sime dimension on other browsers like Chrome, check this http://d.pr/i/XTGe Is someone here who can confirm that on 'real' IE ?

Thanks for forwarding those screen shot measurements, coming in at 1000px. I would like to see what IE9 and firefox are coming up as from someone out there, since those for me are coming as 1100 and 900... could be something just localized issue on my pc ??, would be helpful to confirm...

If you use cache it can be a cache issue also browser cache. Please try to remove temporary memory and always use CTRL/CMD + R option to refresh your page.

I cleared firefox cache (on pc), options>clear cached web content, then refreshed with CTRL R. I also check control panel>temp internet browsing history and setting and confirmed my site is not showing on the list there.
Still the site shows up 900px on FF on this laptop. IE9 uses Temp Internet Browsing for cache so nothing that would result there on it showing as 1100.
I feel foolish not understanding why it's happening, but just don't understand how to fix it?

So you see the site on FF and IE9 coming to you at 1000? It would be good if I can confirm that... atleast I can know the site is out there correctly.

I also did global clean sweep checkin>clear cache>purge expired.

On my firefox it is definitely 1000px wide, please look at the screenshot >> http://d.pr/i/VxVX in top left corner you can see dimensions of measured area : 1000px

Thanks, found out the pixel ruler was the issue. Downloaded the mozilla addon and got the same. Thanks for the help!