Firefox misplacement of form

I have a form that is supposed to show in the center of the page (using 3 collums) but it is instead showed all the way to the right ONLY in firefox, with the rest of the page continuing as it is supposed (in the center of the page).

Any clue why this happens? (note: I'm using a CMS, but I have similar pages showing just fine, that uses same setup and same styles etc.)

Firefox and IE side by side: Firefox misplacement album(imgur)

The site that isn't working properly on Firefox: http://ift.tt/1CyXkZN

A similar site that is working properly on Firefox, click the text "Tegnekonkurrence" in the left sidebar

Edit: forgot to mention that i used Firefox dev tool (F12) to resize the right hand image so that you can see that the input fields are hiding there and not just "gone"