The English-language Wikipedia will be in read-only mode for maintenance tonight/in the morning starting around 9pm PST (midnight EST; 5am GMT; 6am most of Europe; the rest of you are on your own).
I'll be making some slight alterations to the database structure and installing an updated version of the software to better support client-side web caching for more browsers (so your browser will reload pages only when they've actually changed instead of every time you visit them). This will also enable a future update to do server-side caching which should reduce server load significantly.
IE users, this should fix the cache bug where red links remain even after a page has been created; the page should automatically reload with the correct link status.
(This update has been running for about a week on meta.wikipedia.org and test.wikipedia.org with no complaints so far.)
This will require taking the wiki "briefly" into read-only mode while alterations are made. I don't know exactly how long it will take, but don't be surprised if it takes about two hours. These things always take longer than hoped. :)
The other languages will also be done around this time, but should go much faster; there will be brief read-only outages, one at a time.
-- brion vibber (brion @ pobox.com)