+font button and - font button

I like to give three options to reader about font size.

One is default font size.
Second one is + font size.
The third one is - font size.

I see some websites which is written in my own language provide these opstions.
But I don't know any English sites which give those font size options.

Do you happen to know any English sites which give those font size options?

Can Javascript give these font size options?

Take a look on this site it may be what you are after

http://www.dyn-web.com/dhtml/sizefont