Applies PR blocking to outgoing links, to reduce the incentive for comment spam.

zem_prblock is a Textpattern plugin that reduces the incentive for comment spam by blocking PageRank on outgoing links. It also allows attributes such as class and target to be selectively applied to links to external web sites.

Comment spam is usually motivated by web site owners trying to improve their ranking in Google search results. They do this by including links to their web site in comments submitted to many different blogs. Google interprets these links as meaning that the spammer’s web site is very popular.

zem_prblock works by ensuring that Google ignores links to external web sites. It offers two different methods: javascript redirection, and the just-announced rel=nofollow technique. The plugin only effects links within a predefined block, and skips local, relative and ‘mailto:’ links.