At the bottom of the wp-admin, when going to settings --> WP Super Cache, at the bottom of the page, you'll see this:
WPSCMin, a Supercache plugin that minifies cached pages by removing whitespaces and extra characters
Yahoo! Yslow is an extension for the Firefox add-on Firebug. It analyzes web pages and suggests ways to improve their performance based on a set of rules for high performance web pages. Also try the performance tools online at GTMetrix.
I already use Google libraries and test often on Yslow and Gmetrix, but I went to the link for WPSCMin, and it's not a valid plugin. I uploaded it manually via the file manager in my host's Cpanel. But WPSCMin tells you to download minify-2.1.5, and again, that's not a valid plugin, and it would take hours to upload it using the file manager. So I'm leery of messing around with it.
Should I just open up an FTP connection, like WS_FTP, and upload the entire folder? Or is this information inaccurate, and should I just ignore it?