This is took straight out of the FAQ section:
How do members include links or images in their messages, comments and forum posts?
Currently there are a few different methods to include a link or an image in a comment, message or forum post. It is recommended that you learn the method described here since Newschoolers will one day use it exclusively.
Comments, forum posts and messages are stripped of all disallowed HTML tags upon submission. This means if your comment, message or forum posts contains an HTML tag that has ben disallowed it will be removed.
Disallowed tags include: img (image), a (link), font, table, meta, etc...
Including a link is now very easy. Simply type out the url for the link and it will be automatically made into a link! No more messing with the tags.
To display an image simply type out the address of the image between [IMG] and [/IMG] tags. As example:
The above text will be replaced with the image. This will only work if:
1. The image address is preceded by [IMG]
2. The image address is followed by [/IMG] (with the /)
3. There is no space between the IMG markers and the image address.