How do i do this on the roblox website?

[LuvvReal (gdyutegoldie)]

How do i stop everyone from appearing offline on my friendlist even though they arent

[iicloudsforeveriii (cloudy)]

This seems to be a bug. I suggest making a bug report for this. A bug report did exist for this but it has now been closed, so you can safely report it would having the issue of your report being a duplicate.