Does the browser support to set font of the webpage?
I found nothing about it.
Can anyone tell me?

Go to about:config url or Edit -> Configuration -> Browser configuration, and change values of prefs:
font.default.x-unicode
font.default.x-western

K-Meleon in Spanish

I found it.
It's in the item of "Browser Configuration".
There are a list of parameters that can be modified, including font.

But no a dialog to do the execution straightly.