You can find the file on wizards with a google search - looks like it sent you to other content but its a 500 line of code file so it could have done a lot more as well (trackers, etc.), way to sleepy to try to figure it out though :) - perhaps someone in the other hemisphere can give it a read through whilst I sleep :)
From what I remember poking around the site back then they were just silly easter eggs, other content like the Masked Mage said or a picture of some treasure.
If my memory serves, I think the "Secret Door" was an Easter egg of some sort and it took you to another page within Wizards' D&D site back before the onset of 4e and the restructuring they did of the site.
"Sweet water and light laughter until next we meet." - traditional elven farewell
Please forgive any spelling and grammer errors, as my android touch-screen phone has no spellchecker. If I do make a grammer mistake, please let me know and I'll try to fix it.
New laptop, still trying to sort my "scrolls" on its shelves...and when will this cursed thing stop doing things I tell it not to?