Images on Portal

Hello , I added some Images on my forum's Portal , and my problem is: After I put some Images on the Portal , and then 1 or 2 days later become like this:
I Don't know why?

All I can say is:

1. Check if the image addresses are still valid
2. Check if there's an HTML error

Of course the Imagess Addresse is Valid , they are worked before 2 days ago , and now is like that. So how can I check the HTML Erro?

By checking the addresses of your images, keep landing on an internet page with written

UserbarsMaker.com [Version 1.0b]
(C) Copyright 2006 Nightmare
C:\>cd http://userbarmaker.com/temp_userbars_shack/411194846455.png
Error 400
Press I to return to the Index page,
C:\>

As for checking HTML codes, you simpy go to the lock of th portal (through the admin panel) and check to see if the tags are opened/closed properly