You see them all over Neocities. If you're new to this website then you might want to learn how to make your own. Lucky for you, they're very easy to make!
Buttons are kind of the most common web thingy you see on Neocities. They're also my favorites. They're great alongside one another, stacked, or arranged like a set of bricks. IMO, web buttons fit in everywhere!
Buttons usually have a gray rectangle as a base, but it isn't required. The dimensions of a web button are, most of the time, 88x31 in pixels. (ALSO can I just say that's so weird?? 31 is such a non round number... it should be 32 and 88 since they're both multiples of 8. But whatever.)
Here are a few bases that can help you out if you don't know where to start:
The best kind of image editor when you're making a button is the kind that is specifically used for pixel art. The one I use is Piskelapp and also Aseprite. Piskelapp is free and online, and Aseprite is a downloadable app that comes for a price (not something you have to pay for every month though...). Since web buttons are relatively simple Piskelapp should work fine, even though it has less features than Aseprite does.
Here are some small graphics that you might draw inspiration from or use in your web button:
There are a lot of graphics like these all over the internet! If you look for a web graphic you want, you'll probably find it somewhere. If not, you're welcome to make your own.