Jobs & Experts front end modify

Hi there!
I would like to add 'http://' in front end company form (1.png) in order to avoid the error message (2.png). Which is the php files where I can add 'http://'?
Also, when I try to upload images or files for extra information field the pop up windows doesn't work properly. For each file I've to open it 2 times.
Moreover, is it possible to have a preview for the uploaded images in extra information field?
Thanks a lot
Cheers,

Marco