Just tried out your plugin, it looks quite promising. Curious, are there any possible conflicts with WP Better Security that may cause it to not work properly?
I have followed the tutorial but the frame and dropshadow are not showing in either Firefox or Chrome. However, when I check the code using Firebug in Firefox, the code is there for a border, yet I see nothing to support the dropshadow. It would appear that the border is there but invisible because it's white on white.
Any ideas why the drop shadow is not showing? Bearing in mind that this is a very early work in progress, you can see a bit here: