Sleepy, just do what I said and it should work for you.
EDIT: I think I know what you are doing. I did the same thing.
Just delete everything in between the two sets of brackets. What's inside each set of brackets is what's known as BBCode. Simply highlight both of the bracketed bits of BBCode and THEN click the icon that looks like a little globe with a tiny chain on it. A window will pop up for you to paste the Raverly link into. When you've done that, click "Okay". You should see a line of code with the link to your Raverly in between the bracketed bits of BBCode. Click Save Signature. Now you should have a clickable image in your signature, which links to your Raverly account.
My knitting blog: Yarnolicious
Oceanblue28 on Ravelry
Garter Stitch Scarf in lavender
Garter Stitch Scarf in variegated shades of blue