Google has added a new undo feature to its mobile Gmail web app.
Now when you use the Gmail mobile web app, youll have a small window of opportunity to undo four key actions: archive, delete, add or remove a label, or move a message/conversation.
When you take one of these actions, Gmail displays a yellow bar that recaps what you just did and allows you to undo it
You can try it out by visiting gmail.com on your mobile device.