[TYPO3-english] How to pass a parameter through a whole TYPO3 site in 4.5 respecting caching?

[Stephen Bungert]

Then I think linkvars is all that is required

That passes on these links.

config.linkVars

I use that with google analytics tracking variables across several sites 
that I run so that I can see if someone goes from one of our sites to 
another after clicking on a link in an email.