Players may not leave the table during the play of a hand.
There is just one exception to this and that is if you immediately notice that the bid that you have just made is not the bid that you thought that you had made.
See Law 25A ( see Related Link below ) in the Online Laws section for mis-clicking a bid. It should be impossible to mis-click a bid using the new Java version of the program and this should only be a potential problem for those using the original Windows version of the program.
You may only use this dispensation to correct a mis-clicked bid and not to change your mind about a bid.
However, if you mis-click a card during the play, you may not attempt to rectify. If you are worried about mis-clicking a card, you should instead click/tap the card once to detach it and then again to play it.
See article on the BridgeClubLive web site