"From 9am, we'll be posting at least every hour. You can look forward to video, guest posts, pictures, diagrams and anything we can lay our hands on as the day unfolds. We'll be talking to (and capturing) the BBC people who play a part in the complex iPlayer process.
And, in the spirit of all things social media, we'd like to invite everyone to take part.
Are you watching iPlayer at home, at work or anywhere else? Take a picture, and add it to our special iPlayer Day Flickr group - we'll publish the best and most interesting on our site.
Twitter legions, let us know what you think of the iPlayer, its programmes and features, by tagging your posts #iplayerday. We'll be streaming them live on the blog. Twittering BBC staff will be taking part all day too.
At around 11 on the day we'll be catching up with Erik Huggers, director of Future Media and Technology. Erik has agreed to answer some of your Twitter queries and we'll be posting his answers online. So if you have any ideas you want to get off your chest, Friday really is the day to do it."