Multiple IPN URL -- 2

I have 3 websites: 1. [login to view URL] 2. [login to view URL] 3. [login to view URL] And they all have diffrent IPN url's, but the problem is that paypal only accepts one URL in their website, so im stuck here and don't know how to solve this problem. Customers should be able to pay anywhere on the 3 sites, and the payment should come to one account. And most important of all: I need instructions on what you've made, and which files etc have been affected, so i can redo the same procces later on, if i update my website and loose the changes. The second problem is, as you see on each site, there is a Button saying "Tilføj Annonce" i would like some help on how to change it's colour to Yellow, with a hovering effect.