Thank you Wei for the comment on my website, and the info on the sidebar! I will have a look right now.
Edit: It was the listing_details_sidebar.tpl Edit 2: Did someone make a change to that sidebar area? I renamed the file (listing_details_sidebar.tpl) to remove it, but then I am unable to use the sidebar for the categories content box. I have did a refresh -> AP -> Common and I clicked all of them, still no luck.
Edit 3: I fixed it, it had to do with a style I changed. and it also affected the post ad page.
Thanks again for your guidance!