Yup, deleted history is a big teller - why delete it if there's nothing to hide? (The common excuse of "to clear up space on the computer" is a crock...the history files don't exactly take up megabytes, so if his computer is in that much need of space he really should get another hard drive!)
Snooping, I wouldn't encourage - I know as partners of PAs we've all done it, and yes it's proven us right about our intuition time and time again...but at what cost? Beyond confirming suspicions, I believe that ignorance may well have been bliss. But it's usually too late for that by the time people (myself included) find this site, as the obsessive searching and looking at all the sites our PA partner has visited has usually been almost as damaging to our psyches as their addictive behaviour itself
So all we can do is try to control our desires to snoop in the future...and that's where accountability/site-blocking software actually
can be good. You get copies of what sites have been visited on the worrysome computer, and the pa knows that you will see what they've been doing - for someone who's honest about being free from their p addiction it's simply another way of reassuring their partner that they are being truly honest, and it can also provide a "last resort" safeguard if required. My advice would be to use accountability/blocking software if you can...but don't visit any dubious sites noted if you can avoid it, as the images won't fade easily from your mind and they will make it that much harder to move on.
And for the record, the desire...need...to snoop and be reassured one way or another about your partner's internet destinations does fade over time, if your husband/partner is willing and able to prove their trustworthiness and honesty. As long as honest communication is put first in your relationship, time DOES help to heal this wound. I've had to fight myself from digging sometimes also, but thankfully over time this desire has faded. The best advice I could suggest for how to get over that desire is similar to what many PAs say helps them - honest determination to win this mental war, mixed with plain and simple busy-ness: Do your best to replace negative thoughts with positive ones (it can take a lot of practise), and don't give yourself time to worry.