My blog got ranked high doing nothing!

My general internet blog called Bogart's Online World have made a surprise for me. In a month, I did not perform web optimization anymore because of poor performance of promoting my pay-per-click ads like Google Adsense, Bidvertiser, Smowtion as I earn not much as I expected. Today I have checked my blog again and there are still comments which are stored unpublished, so I publish them because they have good comments like no other. When I check it using my Seoquake tool on Mozilla Firefox......I was really shocked because it came from out of nowhere from no rank to PR3. I can't believe it. Even I don't perform web optimization in my general internet blog, it's a miracle like no other that mu blog's PR got higher.