Oh great! we have a UK divorce lawyer in our midst

If your spouce is using your computer to log into the site in question you could always try a keylogger and catch the password next time he logs in.
That's when you commit a criminal (as in "felony") offence.......................

If I have legitimate access to a computer, and there is a link that I just have to click, then it has been left in "plain view" and I would get away with it provided I caused no damage and did not engage in other criminal activities as a result. Consent to view is effectively implied?

Using a keylogger is not allowed, even on "your" computer............ (and property ownership in a marriage partnership isn't clear cut)....... when it is used as a means of accessing the PRIVATE account of another individual without their permission. Remember, the account is NOT ON "YOUR" COMPUTER, it is on someone else's, and you don't have permission? In several countries or states this would be legislated against as "unlawful access"........... in the UK, try the "Misuse Of Computers Act 1990"

http://www.opsi.gov.uk/acts/acts1990...00018_en_1.htm

I don't like the fact that the OP was not honest with us in the first place. Also:

I stupidly put a different account in the same site, and since then the original login details have disappeared.
Same site name + same IP address would doubtless get it overwritten?

And:

so, cant reset the password without him knowing.
Or without knowing the original password, and commiting a criminal offence...........

My advice is go see a divorce lawyer before you dig a hole that you can't climb out of..............