Using a transparent gif to create empty space is lame because it's cross browser compatible. All the cool kids use the spacer tag.

Spacer appears to be a remnant from the old days of Netscape circa 1998. In 2006, it appears to only partially work in Firefox -- only the "block" type seems to do anything, the horizontal and vertical spacers don't seem to have any effect anymore.

I couldn't get spacer to do anything in IE. Presumably, it's unsupported in other browsers as well.