Pale Moon

Pale Moon offers a web browsing experience with carefully selected features and optimizations to maximize browser speed, stability and user experience, while maintaining compatibility with thousands of possible Firefox extensions. The browser does not change its graphical environment, so the controls are always in place as you are used to them, and the environment is identical to older versions of Firefox.

The English language can be installed using this tutorial, in the about:config settings, specify cs-CZ under general.useragent.locale.