I have an IT background but am new to Web development. For this project we will have group of 300 invited people (their details to be stored on MySql) who we would look to email every month or so for them to answer questions on how they feel about different Local Government issues. I would like to use Php to send out emails (I think I can do this), each of which will contain a link to our site (i.e. a page containing the questions). I would like this link to be "personalised" so that I will know who each person is when they answer the questions(and submit their answers). Naturally I only want the 300 people to respond - i.e. nobody else. Can anyone point me to a book, web site or give me an idea of how to go about this?