Updated web application hacking page

[Duff]

I added a link to a page that Henri sent me that has a bunch of good
background on Cross-Site Scripting attacks and some test strings that
can be used.

Also, I wanted to let you all know that this is a FORUM, meaning that
anyone can contribute. I welcome you to do so. If you write a research
paper or find a new tool or technique that you think is cool, please
share it with the group. Anything that can be useful in terms of VA/PT
work is more than welcome. If you run into any technical issues
posting stuff to the pages please let me know.

Cheers,

--Ian