I had decided to create the "glass" effect popularised by OSX and Vista and while following various guides and creating some graphics in the GNU Image Manipulation Package I spotted a pattern and decided to come up with a way to create the now popular glass effect in CSS, without using any graphics at all.
Using the gradient fill in GIMP and applying those colours to the CSS used to create the Nifty Corners effect, I managed to create some pure CSS Glass buttons. Hopefully I can explain how I did this below and show you how you can create the same effect for your own projects.