Bilingual site

I have to make a bilingual site and i really wanted to know how to do this.
The most simple solution is to make two different versions of every html file, but it is not flexible and it would consume storage space.
the other way would be in an intelligent manner, which is, for example, replace via script the text between the tags, from a xml file.
how can i do this? how can i replace the text of a specific html tag in the DOM with a specific node from a xml file? could you give me some hint?
I would really apreciate it, thanks