Spam report while signing up

Hi, does any one know why some users while trying to sign up get this message '' Sorry,it looks like you are trying to submit spam. If you believe that this is a mistake please submit a false report here htt://mywebsite/contact.php''

They could be trying to insert URL's in the description box.

If your able, ask them what it is they are using to sign up with.

Also very short words can trigger the anti-spam features.

Thank you,will definately work on that.