Okay my lecturer asked me to come up with a website that has a handshake(this happens when someone logs in then a link is sent to his email address so as when he clicks it,it will take him to the website).
There are networking handshakes, as EvolutionFallen discussed, but they are different from what you seem to be asking for. (A networking handshake really has nothing to do with emailing upon clicking a link). What programming language are you using in class??
CSS is just used to aesthetically style html markup.
OK so you will want to create an HTML page that has a link, and upon clicking that link, loads up a PHP page that sends out an email. I suggest reading up a bit more and then posting in the PHP forum with what you've tried so far and where you're stuck.