Detailed instructions:

This facebook skin currently only works with the Firefox browser. It will make facebook display using the specified color scheme when viewed from your computer only. It will not effect how others see your profile.

1) Get Firefox if you don't already have it: http://getfirefox.com

2) Install the Greasemonkey extension:
https://addons.mozilla.org/en-US/firefox/addon/748

3) Restart Firefox browser to complete the Greasemonkey installation

4) Get the Skin: (Click on "Install this Script" on the right side)
http://userscripts.org/scripts/show/22613

5) When the installation window window pops up, wait a few seconds, then click on the "Install" button.

6) Close any Facebook windows you currently have open. When you reopen Facebook, the valentines colours should have replaced the old ones.

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Note: To turn off the script, simply right-click on the monkey head in the bottom right corner of the Firefox window and un-check the "Valentines Facebook" option.