Well its complicated to make one. You would have to find the "Login" button in the HTML, and then make it so that instead of redirecting you to the website or something else, it redirects you to a FLP, which would require you to make the link something like "flp.html" instead of something like "officialloginscreen.html" Next, you would have to make the login on the FLP steal the Username and Password entered by making the POST Data go to a .php file, where the PHP code sends it to a text file.

Extremely complicated.

If you want a little more help than I have, ask Bradley. He made a Runescape phisher before anyone else, so he'll probably have more knowledge than me and the mini tutorial I just posted was horrid.