Three mistakes Yahoo made

Now we see once a giant Yahoo, foundering. Once known for its messenger, search engine, mail and finance portal is known for nothing now. I hardly remember if I visited yahoo.com even once a year.
In the wake of world racing ahead of Yahoo and economic slowdown, bad luck that marred Yahoo during tech burst of 2000 never ditched Yahoo. All in all, Yahoo made following astronomical mistakes, which in my view may cause it to see lowest grounds.

1. Not buying Google, and not getting sold to Microsoft: Yahoo had an option to buy Google in 2002 but I don't know what made them not buy it when Google already took yahoo's place for search engine. Then quite recently, yahoo rejected when Microsoft initiated a buy out step. Now Yahoo's stock prices are below 63% from what Microsoft quoted.
2. Following instead of innovating: Yahoo kept following the king Google in almost everything. When the brand 'Google' had established trust and fame, copying was not at all an option. Innovation could have been the key to their survival. Not that they did not try, but all their projects turned in sour investments.
3. Poor strategies: Advertising was Yahoo's core competence and strength, against which Google's victory is amazing. Here too Yahoo helped Google by not purchasing the ad network, while Google jumped upon the opportunity.