How to make a "Donate" function with bitcoins? I understand my bitcoin wallet generates a new receiving adress everytime i received a transaction. I would like to add an adress to my website for donations. How can i get an adress that doesnt change?
You can just take any existing receiving address or create new one. Any address can accept unlimited transactions count.

Bitcoin clients generate new address every time you want to receive for anonymity reasons. In case with donations you don't need this.