HTML | How to create Page Templates?

(How) is it possible to create a "Template Class" for HTML?

I created a Page that leads to subpages, which should be the same, but every has it's own text.

Example:

Simply I want a class that I can "inherit" from, that I only have to change/insert the messages and don't have to copy the completely code into every new class.

(Sorry, for my bad English.)