Funny enough, I don't remember precise websites that really changed my life - usually they would trigger a flurry of activity and would be forgotten themselves.
I don't remember where I read in 1997 that being gay is 'okay' and normal - but that was a major revelation for a geeky teen in a notoriously homophobic and close-minded country (no more suicide attempts for me, yay). Co-incidentally that led me to work hard on improving my English, as all information was in it.
And my improved English led me to start my own website - the only website that changed my life and I still remember all the details of it (even though it is no longer online). It was dedicated to my hobby project - the project that led a foreign company to hire me and relocate me to a Western country. Which triggered a chain of events that brought me to the UK, to a much happier and fuller life than I ever hoped to have.
And finally, I don't remember where I read an article describing the author's struggle with an eating disorder, but I realised that I'm going through exactly the same thing and that I need help. It improved my life dramatically, pretty much kept me alive - but I don't remember what or where it was...