Information on how to create a firewall using ipfw is hard to come by. I’ve found bits and pieces of useful information in various places. I’m working on creating a tutorial on how to configure ipfw for Mac OS X, but in the mean time, here’s some information on the extremely low-level internet packet, ICMP.

I started this exercise with a simple bordered div which contained four divs that each had a background-image and that were positioned in each of the corners. This worked great in Mozilla 1 and Netscape 6, but not anywhere else. As I fixed bugs in each of the other browsers implementations, I ended up with this code.

This hack can be used to hide CSS from Opera (versions 5 and below):

html>body .myDiv { m\yProperty: myval; }

This hack can be used to hide CSS from Opera (versions 6 and below) and from Internet Explorer for Windows (versions 6 and below):

head:first-child+body