A potentially dangerous Request.Form value was detected

Some articles related to this error message, and useful for further investigation:

http://blogs.madtechnology.net/blogs/chris/archive/2004/03/20/366.aspx

http://www.asp.net/Forums/ShowPost.aspx?tabindex=1&PostID=388929
http://www.asp.net/faq/RequestValidation.aspx
http://www.aspcode.net/articles/l_en-US/t_default/ASP.NET/A-potentially-dangerous-Request.Form-value-was-detected-from-the-client_article_147.aspx
http://www.dotnetjunkies.com/HowTo/3ABCD244-CC7C-4CED-B64E-BCF05191CDAB.dcik

http://www.mikeschinkel.com/blog/APotentiallyDangerousRequestFormValueWasDetected.aspx
http://kbase.vircom.com/Novo/default.asp?id=1041&Lang=1
http://forums.microsoft.com/MSDN-BR/ShowPost.aspx?PostID=743559&SiteID=21
http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=544937&SiteID=1
http://support.microsoft.com/kb/821343/
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnpag2/html/PAGHT000003.asp?_r=1
http://msdn.microsoft.com/msdnmag/issues/04/12/WebQA/