If you are using skype on your Nokia N900 and go to “Availability” option, you won’t find any status to make yourself invisible. However you don’t need to worry, you can create new status with few taps.
To make more statuses other than the default ones, follow these simple steps.
Open your skype application on your Nokia N900 and go to “Availability“. On the right side of screen you will see “New Status” option, and tap on it.
In the field of “Name” type whatever you want like invisible, out of sight, etc.
Step 3 (optional):
You can also change the icon for new status. Tap on the icon and a list of available icons will be displayed. Select any of them.
Now tap of Skype account and select the Invisible from the list and save the newly created status. The status will be available on “Availablilty“. Tap on the status to make yourself invisible to your friends with one click.
Also you can use the steps described in this tutorial to create other custom statuses like “Away“, “Do not disturb” or “Offline“.