Now a days ,there are large number of applications and services available on web to track your online or offline status activity of your yahoo ID.
If you want to pretend your self offline to all these applications from where your friends or buddies would be tracking your online offline status , you just need to set a simple option which is available Account Information Section of your yahoo id.
Let see how can check that option which says: Check the box to hide my online status ( ) from other users.
Follow the procedure given below
1. Login to your yahoo mail and click the link options ( above all mails in the right top ).
2. Click Account Information from the links in the sidebar left.
3. Click on the Edit / Create Profile link in the right sidebar, a new window will open up.
4. You will see a check box which says: "check this box to hide my online status from other users" as shown in the image below.
5. Check this option to hide your online existence on yahoo from your friends. If you check this option there will be nothing on web that can track your yahoo online / offline activity or time.
We hope this small tweak will help. If not then please let know through comments.