Div gets too wide when 1 column is removed

I'm doing Wordpress theme based on layout that wasn't done by me. The layout originally contains 3 columns, 开发者_JAVA百科and works fine.

But when i try to remove one column to get 2-columns for content pages, the layout broke, and the #keskimain gets from some reason 2px too wide.

http://tietojohtajakilta.net/wordpress/2-col-test/

What's the reason for this, and is it fixable?

I made a quick adjustment to following:

#keskivas {
   width: 71px;
}

#keskioik {
   width: 62px;
}

That lines them everything in up in Firefox. I cannot verify if that will fix your problem in other browsers, however. For future reference, Firebug is a very handy tool to help troubleshoot these issues.

EDIT: also setting the following without the above should fix the problem too.

#keskimain  {
   width: 970px;
}