Filter a form before submit (stop spam)

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Bids
15
Avg Bid (CAD)
$112
Project Budget (CAD)
$30 - $250

Project Description:
We have a form which give the possiblity to visitor to let message.
You can see an example at the end of this page:
http://cfcoaticook.com/avis_deces/product_info.php?cPath=27&products_id=305
The actual script is based on "reviews" that exist in OScommerce.
The whole system is based on Oscommerce.
The problem is that even with re-capatcha, spambot succeed post spam messages to our database.
I would like to block these spambot.
I was thinking to block submitted messages that contain "http" or "www" in text content.
People that post message in these webpages doesn't use URL.
Maybe we could add a javascript alert to people that are trying to post an url in their message saying that they cannot type url.
If you have another suggestion, I'm open.
But there has been many trials by other programmer to stop spambot without success.

Skills required:
Javascript, MySQL, PHP
Hire benlaf
Project posted by:
benlaf Canada
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