Either you have Javascript disabled or your browser is getting on a bit.
First, check you have Javascript turned on.
Look up 'Javascript' in the help files that came with your browser and you should find simple instructions for enabling it. If you have a problem, email us or post on the boards.
If that doesn't work...
We suggest you download an up to date browser. Our favourite is Firefox and it works like a charm on both Mac and PC.
You could also use Microsoft's Internet Explorer 7 although we still don't think it's as good as Firefox. It's only available on PC too.
You can still post the old fashioned way, typing the various tags out by hand. Click 'Next page' for more on this.