Straight donations probably won't earn that much.. They never did for me BUT.. If you give something in return for a donation as a 'thank you' you can do very well.. at the beginning of this year i was earning between $1,500 and $2,500 in donations with "thank you's" - the thank-you being access to a restricted forum area with info that the visitors wanted....
if i earn from donation, can i put adsense ads on my website? will they dont want to donate because the ads?
Was not a problem for me.. but i dont do 'straight' donations.. Everybody gets a 'thank you' of some sort.
He said that you should give something in return to your users, like some "New features"/"Access to restricted areas where users need to go" to users donating you money. and Yes you can place Adsense ads - Removing ads to donating users is also a considerable feature to Donators