A number of top websites have gone "red" for World AIDS day - Twitter, Facebook and Google have all given space on their pages to the (RED) charity which works to fight the spread of HIV in Africa.

Twitter is perhaps taking the biggest step - they have a @joinred account which claims that users who write Tweets with #red or #laceupsavelives in the message will find that their tweets are turned red on the microblogging site. Unfortunately that won't extend to third-party clients.

Facebook has a (RED) fanpage which has a shareable video, instructions on how to change your Facebook picture to one of several (RED) logos, and a shop that contains products from brands like Starbucks, Gap, Apple, Dell, Armani, Converse and Hallmark.

Lastly, Google has given the charity a link on its ridiculously-high-traffic Google.com homepage. The link, which has been used to advertise Google products like Gmail and Chrome in the past, says: "World AIDS Day: Learn more about how you can help", and links to a page on Google's philanthropic wing, Google.org.

How are you marking World AIDS Day? Let us know in the comments.