By default, Gmail sets your idle or availability status to “Available” as soon as you log in to the email site. The “Available” status also has a green circle icon next to it to indicate you are visible to other Gmail or GTalk users in your address book or contact list. You can verify this by locating your full name under the Chat and SMS label on the left side of your Gmail account page. If you leave the Gmail account page open, but do not compose or access messages in your inbox, or if you don’t use the chat feature, the availability status changes to “Idle” automatically after 15 minutes. If the Gmail application sets your status to “Idle,” you will see a yellow circle icon next to the status label.
Sometimes, you might just be too busy to answer support questions except for those from paid-support customers. Using this example scenario, you might want to create a status message that reads “Available for Paid Support Customers Only” or something similar. You can create this, or any other message, easily by clicking the drop-down button next to the status label, and then clicking “Custom Message.” You can then simply type in your custom availability message and press “Enter.” From that point forward the new message is visible to all other Gmail and Gtalk users that have you in their address books or contact lists.
GTalk is the desktop client version of the Gmail chat program. GTalk allows you to chat with others in your Gmail address book or contact list even if you don’t log in to your email account on the Google website. Like Gmail chat, GTalk allows you to change your availability status easily with a drop-down list or create custom availability message much in the same way as you would on your email account page. If you have both the Gtalk client and your Gmail account page open at the same time, the two applications share your current idle or availability status. Therefore, if you set your availability status to Invisible in Gmail, your status in GTalk updates automatically. The same is also true if you change your status in GTalk; your Gmail availability status changes automatically.