Recently, we have had a couple people in our Lab Hours who are having issues with their site not seeing the style sheet. For example, one member went to their site and clicked edit CSS but could only see the admin_menu.css, Embedded Styles, and a long bf025e070697f5bc5ac0681ae3c2624c.css file - NOT the style.css file.

Jer Davis gave a good reason for this:

"Drupal has a performance setting that takes all of your style sheets, all of your module's style sheets, and all of it's default style sheets and shoves them into one super compressed cached style sheet. This makes things faster for users accessing your site, however it's a real pain during development as your changes don't show up until the cache is rebuilt.

To fix this, go to Site configuration > performance and un-select the CSS compression setting. But be SURE to turn this back on when you go live! :) "

Thanks, Jer!