Enter the URL of any CSS file to view and modify its color spectrum
I present you with the CSS Stress Test bookmarklet.
CSS Coverage is an extension for Firebug which allows you to scan multiple pages of your site to see which CSS rules are actually used in your site. This extension requires Firebug.
When applying CSS3 inset box-shadow or border-radius directly to the image element, the browser doesn't render the CSS style perfectly. However, if the image is applied as background-image, you can add any style to it and have it rendered properly.