Does anyone know how to create multilingual websites?

I've only created a few multi language sites and there may be a better way, but what I have done typically is recreate the same page in the other language. For instance if the text on the index page (http://www.mysite.index.com) is in english and someone wants french, they can click the french flag which acts as a link and takes them to the french page (http://www.mysite.index.com/fr) for example. As far as having the language dynamically generate based on language not to sure. Maybe google has some kind of API for language.

I've created a couple of by-lingual sites before, in English and Gaelic. I used ExpressionEngine to build the sites and used an add-on called Transcribe to deal with the language switch.

Basically how it works is you set variables for static pieces of text and when the user switches languages the add-on takes care of translating the static text. You then have different versions of editable content in each language, for example an about us page in English and then the same page in Gaelic and when the language is switched the appropriate language variation is displayed. The add-on will even translate the name of your templates - if you are using EEs template structure - and also switch out the url.

It was a huge learning curve when I designed and built them and there were a lot of questions that came up, e.g. meta-descriptions in both languages but overall the add-on was fabulous, as was the support from the developer.

I am sure there are many other ways to go about it but this was the route I went down. Hope this helps.