I take it you mean have a link that will send an email to your friend.
Well you are going to need a form that the user fills in with some minimal details like the friend's name and email addy.
Now the only way to process this in pure html is with a mailto link . You will need to use javascript to capture the friend's email addy from your form and insert it into the link dynamically. A mailto link works through the user's own email client. All in all this is not the simplest way to do things, and not very neat to for the user either. So "simple html" would not be the best.
Far better to have the form submit to a php script that generates the email adn sends it with the mail() function. Probably a lot easier to code than all that js, looks neater as it does not fire up the user's email client, and allows you to monitor who is refering whom, and what the outcome is.
