Rick - the site works fine for me in Firefox...
VanB - Yeah but how are you going to get the buttons and sticks to respond as key presses? Hardwiring it yourself is a nightmare (not only is it complicated, but the sheer amount of wires is ridiculous, 2 for every microswitch, thats one on every button (prefereably you want at least 12 buttons AND 2 starts, 2 coins, and a menu/esc button) and 4 on every joystick!
An IPAC is an easier solution, but they'll cost u at least 30 quid, plus all the wires etc. There are some people who sell homemade pre wired kits ready to solder/clip onto your microswitches, but again, its 30 odd quid and you still have the ightmare of one wire being on backwards and the whole lot doesn't work
I've made lots of Mame cabinets, and buying separate components IS cheaper, but only just - one time i paid the extra 20 quid for an x arcade and just ripped it appart to save myself the headache of wiring it all
A cheap and good alternative is to get one of the dreamcast, psx or xbox arcade sticks made by Sega or Namco with genuine arcade parts second hand on ebay - they are much easier to hack, or even get a usb converter for a tenner