Sending a URL in my parameter list

Hi:

I'm not a php programmer but I'm slowly learning out of necessity.

I am sending several parameters to my index.php and everything works well until I try to send a URL.

Then I get a 403 error. I am on Hostgator and their support wasn't helpful because the guy I chatted with didn't know php.

Here is an example of the URL that I am using...

http://00001.example.info/index.php?Property_Address=exampleaddress&Mobile_Listing_URL=http://www.exampleurl.com/

Hopefully there is a simple solution.

Thanks in advance.

Anne