Delete Classified Listings and Subs

For some reason I am not able to delete certian classified listings from the system. I want to clear them out and make my own. I cant seem to even see where to edit the sub categories either. Can someone help me. I have a been working in the Content admin area, and Classifieds, is there someplace else to edit these?

I had no problems to delete every listing and make new one. 
Use Firefox for this sort of things.

Thank you for the input. I actually did use both Firefox (latest version), IE 7 and Safari, doesnt work with any of them.