choose the check box in front of the last message in the desired range.
The messages in between are selected automatically.
snag the check box in front of any non-adjacent messages to select them as well.
you might select another range and remove individual messages from the selection by clicking their check boxes again.
Whichever action you perform next will apply to all selected messages.
Deselecting a range of messages in Gmail works exactly the same way as selecting them.
Once all messages are selected, unchecking any message on the current page also unselects all hidden emails.
The new selection comprises all emails on the current page minus those you unchecked.
