Why does this happen?
 

I really don't understand why my forum collapses on itself when I switch the width from pixels to percentage.... I'm at a loss and can not figure out what the issue is...

Picture below

960pixels is not the same as 90% ... if you set a smaller value than the default value of the navbar or other part of the design, your site width will suffer...

if you use percentage in the width of the site, it will be evaluated depending on the width of the window of your browser, so will be different for everybody in the average usage...

the best solution is to use a fixed value after the default width of your entire content... so if your content is about 900 pixels wide, a good 920 or 940 would do well... you can read about the 960 pixels grid project here: http://960.gs/

I understand the differences between the two.

I currently have that the "wrapper" set at 1150px... I'm toying around with percentages because it just seems easier to adapt to all screen resolutions.. instead of growing smaller and smaller as screen resoultion goes up.. it would always take up 90% width... I notice that a lot of produced themes used percentage values without there themes collapsing, I however can not figure out what I did to cause it.

Can we geta link to the style to view the problem ourselves.

the reason is that all the content inside the theme have to be in percentage to fit the extension of the wrapper... so, all div etc...