You should separete the information about directions to the website etc and put that on a different card. This card can also have the same design as your main invitation.
We had a separate card also (or rather, had the website printed on an insert with a map/directions on it and an insert with hotel information on it). It just said something like "For additional accommodaton informations, maps, and more, please visit...."
We have a Reception Card and we put the wedding website on it with the note "For more information and directions" It is not on the wedding invitation so that rule was followed.
Re: Website on invites