After the interation of Gtalk in orkut you can now easily become online and offline in orkut , if you are online a green buttom will be displayed just before you name but if you are offline the buttom disappear,
Almost half of the orkut users are using this feature in there orkut profile if you dont have this feature then check yours orkut setting in Gtalk tab , there you will find the status of you gtalk integration.
If this feature will not activated you will find below mention message in yours orkut profile.
We are very excited to tell you that a new Google Talk feature is coming to orkut!
We just need a little more time to release it to you. Very soon you will be able to use this feature and this page, but in the meantime, you cannot make any changes to your configuration.