Use <a></a> to do it, but without the http:// at the beginning. For example, if you want it to say "Go to google.com", and have "google.com" be the link, use
Go to <a:www.google.com>google.com</a> . I think that the colors of the links is the \c4 color (teal/turquoise type thing) Also, the color code tags (<color:>) need to have 6 characters, not 5.
Here's the fixed event for the one you described in the OP:
OnActivate > Client > ChatMessage > <color:FFFFFF>Vote for the type of server you want next week <a:forum.blockland.us/index.php?topic=261827.0>here</a>.
This shows up as:
Vote for the type of server you want next week here.