'URL with symbols like ., !, etc.'
 

(The reason why I have "'" in the subject line is just for a test to make sure the apostrophe gets escaped.)

One thing that I saw in the URL of a thread is something like this:

http://www.bikeforums.net/showthread...vers-are-GREAT!

Shouldn't a forum software remove any invalid characters off the URL? When I email to my family using Outlook 2007, the "!" is not included in the URL, so when I went into the Sent Items folder, clicked in the link to the thread that I've provided for my family to look at, it seems that the link works and is not broken. So just for curiousity, why does the symbols appear in the first place?

In an off-topic note, it is important that SQL injunction attack must be prevented in order to ensure the security of the forum, such as escaping the "\", "'", and '"'. If there is only an escape character for '"' and "'", a criminal hacker could work around the escape by using "\" to escape the "\" in order to escape the literal string. (Update as of few minutes later after my post: Well, at least the apostrophe character has been sanitized in the subject line. Pardon my off-topic comment.)