Your comment was held for moderation. When this happens, your comment must be approved by myself or Richard before it gets published.
The general reason that these errors occur from time to time is because I have implemented some strict measure to prevent spam advertising, offense links, forum trolls, and other unwanted content. These measures include lists of blocked IP addresses, and "bad word" lists. In the latter case, certain words, in certain contexts, will trigger moderation for the post. In other cases, posts will get place in the junk folder (but still saved in the database).
In this particular example, your post -- which has now been published, by the way -- contained the word 'free' as part of a link. Specifically, it was part of your image code:
alt="Free Image Hosting at www.ImageShack.us"
Inevitably, with such anti-spam measures, there are false positives -- when legit posts gets held for moderation or junk. It is a small price to pay to avoid having the site overan with advertising and porn, however.
When you get an error message like that, be patient. Richard or I will find your post and approve it.
Another way to avoid these errors is to use the new Optional Authentication (see thread in the Help forum). With this feature, I can mark regular forum members as "trusted". This gives you a free pass, meaning that you will bypass these spam filters. I haven't tested this fully yet, but I believe it should work.