I'm building a website and would like to do some input testing on it.
What are the worst things you can throw at your webform to test if it breaks or handles the failures correct?
Are there values that can cause errors, what should not be entered into the form?
Should prevent XSS attacks.
If your use base is too large check the load of the site.
This site checks a web page for everything
Do load testing. Sanitize your inputs. Go to http://browsershots.org/ and see how the webform looks in different browsers.
Make sure you validate the data the user can send you and that you properly escape all values when you put them into a database or when you send it to any external program.