embed html in foreign website

I would l开发者_Python百科ike to know if somebody knows a method to embed custom html in foreign websites. Maybe there's a firefox extension or something like that (like stylish for example, but for html instead of css)

Actually, that's where the Greasemonkey Add-on is for. Once you have that installed, you can create scripts which manipulate the DOM of any website you would like:

Allows you to customize the way a webpage displays using small bits of JavaScript.

Hundreds of scripts, for a wide variety of popular sites, are already available at http://userscripts.org.

You can write your own scripts, too. Check out http://wiki.greasespot.net/ to get started.

Also nice to know is the fact that the latest version of Chrome, and also Opera (don't know since when, but longer than Chrome) supports userscripts out of the box (no need to install any add-ons).