well, I found many people post alot of comments to wordpress, just to meet a white screen or so, this means that the anti-spam plugin caught their comment as being spam, here's how it does so. 1. Time between the page loading and comment submission. If the comment is posted immediately after the page is loaded, the plugin thinks this is an automated submission. It's supposed that people will take time to read the post before submitting a comment. 2. Occurrence of the "stop" words in the comment text and URLs (comments containing "blacklisted" words like "porno", "viagra", etc. are automatically marked as spam) 3. Quantity of URLs in the comment text. More URLs, more risks to be flagged as spam. The size of URLs in the comment text is compared against the text size. If the whole URLs size is bigger than the size of the text, the comment will be marked as spam. 4. "Spammy" IPs are filtered (if your comments are reported as spam many times, your IP will be blacklisted). 5. The plugin looks at how old the post is and how much time passed since the latest comment on the post. In addition, some blogs can have plugins that give a "DoFollow" link after you leave several comments on the blog. So, you should not count to get a "DoFollow" link on your first visit.