Fix for iframe bug.

A few hours after launching this evening I got two e-mails, one from Frank Arrigo and another from Geoff Appleby letting me know that the iframe code that I was generating was not correct.

According to HTML 4.0 Transitional it must be a binary tag whereas the code I was rendering was a unary tag. I’ve fixed up the code generator on the join page – if you have already pasted this code into your site I recommend that you update it as soon as possible as it can cause problems with rendering on pages.

Thanks again to Frank and Geoff for getting me this feedback!