I thought it was a good idea to ask our guest to RSVP if they were planning on coming to the wedding through a guestbook on our website, but apparently it wasn't as only around 40 people used it for that purpose... Still, some of our friends used it to send us wedding wishes, which was very nice :)
Here is a text that we had on our webpage under a link "Guestbook":
Dear Guests,
Please let us know how many people are in your party and if you are planning to attend the ceremony, the reception, or both, in order to help us with preparation.
Please tell us if you have any special food requirements. We plan to have a buffet-style lunch with Indian Vegetarian dishes and sweets, as well as a variety of fruits and non-alcoholic drinks.
Also, please do not hesitate to use this site to tell us how much you love us and how happy you are for us! :)