Where to edit showpm table width?
 

I think that came from nav bar ...you can set that table with=760 or any number and try to see with number will fix ...look like you set you table with =100% ...but your header is too small .

you can try to deit you header logo bigger and reinstall your header logo .

Is that the only page you're having problems with? When I ran your site through code validation, I see you have a few issues with unclosed and improperly formatted tags which could be causing certain areas of your site's layout to break.

Before forcing your PM table to a certain width, I'd first go about fixing some of those code errors and see if that helps.

could be the postbit wrapper, spacer_open, or just something that is hard-coded in the style