Ad Banner not showing on my server?

I've tried uploading different files, resolutions. file sizes. file types. but it just doesn't show. Everytime I upload something it says "please wait" for half a second and then you see this



I have no Idea how to fix it. Any help?

Oh and I'm also not sure if this is the right place to put this, so if it isn't where do I put questions like these?