Topic awaiting preservation: Checking for Email & URL's in string

I have a textarea, I need to check the contents for a Email address or URL and return an error if found.

Right now, due to not knowing a better way I'm just looking for the following and then returning an error.
1. http
2. www
3. @

Thanks for your time.

AT

Casey / AT
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You want to use regular expressions ("regex" for short) to find URLs and emails within a string. Using regular expressions, you can find only the URLs and emails that are in standard form if you have the right regular expressions.

Here are a few useful links to help you:
http://www.regular-expressions.info/javascript.html - Regex with Javascript.
http://regexlib.com/ - A regex library full of useful regular expressions you can use.