Having been on both sides of the fence concerning this issue when my own marriage was struggling about ten years ago... I can say with confidence "yes you can trust him again" if you both are honest and up front with each other and you see a change in his online behavior.

BTW - make an effort in getting the sex back into the bedroom (say at least once a week) and start to notice your man more and what you liked about him in the first place or as you have seen some one else will and lets face it the human ego is often fragile and susceptible to flattery when we least expect it.