If you want to contribute to the running costs of this site (and you don't have to, it's deliberately free to use and I have no objection at all to people using it for free), then you can do so in two ways:
If you've got spare money sloshing around your PayPal account (and who doesn't?), then you can send it my way. I promise to make good use of it.
If you are one of those people with those new-fangled Bitcoin thingies, I accept donations to:
(I'm reliably informed that if you know how Bitcoin works then the above string of gibberish will make sense to you)