Doh! Not seeing the forest for the trees
SDAITech1 posted while I was writing my message, and he was observant enough to realize you were trying for a link, not an image [slaps the forehead].
Still, the tag probably wouldn't have worked without the quotes. It happens that that URL contains "=" signs, which confuses the browser--it thinks they're part of a different argument. At least my advice about using quotes wasn't completely useless.
--Robert