vulnerability in websites

hi,
how can one detect vulnerability or loophole in a website.

 

Use a port scanner or vulnerability scanners which you can download from various sites and its free.
http://www.hnc3k.com that will have word files that you can read up on, its max 9 pages... and then http://www.elhacker.net has tutorials and those tools for download.

Astalavista!

 

And alot of them...

 

i recommend you accessdiver,pretty good and simple to use.