No, it's not against the rules. You can advertise your site on your signature, blog, or the website section in your profile.
QUOTE
Advertising1:
Advertising any kind of service is not allowed. This includes (but is not limited to): websites, forums, blogs, and chat channels (e.g. IRC, Teamspeak, and RuneScape Clan Chat). Personal messages advertising these services are not allowed. You may advertise these services in your own signature or blog, as long as the service does not break any of our rules, or any RuneScape rules. The exception to this is advertising money making and free membership systems and all kinds of referral systems. Advertising these is never allowed.
Note: The exception to this rule is in the Clans forums, where only links to the clan's website, forum, IRC, TeamSpeak or Clan Chat may be posted, for recruitment or informational purposes.
http://runescape.salmoneus.net/forums/index.php?showtopic=2