What version of Premiere Elements do you have and on what computer operating system is it going to be installed on?
Are you dealing with a serial number or a redemption code? From whom did you purchase Premiere Elements - from Adobe as download or from authorized reseller in box packaging?
Not sure what a web address has to do with all that?
If Redemption Code
If you purchased download from Adobe, your serial number should be listed at Adobe under "My Products" after you sign in at http://www.adobe.com and type in My Products in the Search field there and follow the links to My Products where you find your product and click on it to see its serial number.
Please supply more details.