Officially (unless AB's policies have been changed without me noticing) this site doesn't support the use of HTML coding to include pictures within posts. (However at least one person seems to have managed to do exactly that recently. I still don't know how!).
The recognised technique is to upload a picture to Tinypic (which, unlike most image hosting sites, doesn't involve registration) and then to post a link to it on here:
http://www.tinypic.com/
(Use the 'Direct Link for Layouts')
Chris