Hi, I am trying to set up a link that when clicked opens up your default email program and emails to an address thats in the code, but in the subject field of the email i want the url of the webpage that you are currently on, this can change depending on which page of my site i am on, please help

Then you need to grab the URL with JavaScript/SSI/PHP/whatever. I.e. it takes some kind of programming language or SSI.

Coffee cup software has programs to help you.
visit this link look through the software all have full working trials.
http://www.coffeecup.com/software/
let coffeecup write the code you can then just copy paste your codemod to your pages and helps you learn in the process.

kind regards

See also http://htmlhelp.com/faq/html/all.html#mailto-subject