typo3bloke.net

If you read RealURL manual, you may remember this example about preVars:

'preVars' => array(
    array(
        'GETvar' => 'no_cache',
            'valueMap' => array(
                'no_cache' => 1,
            ),
            'noMatch' => 'bypass',
    ),

....

But think: do you really want no_cache in your URLs? For example, ve_guestbook extension (the one, you see bellow for comments) uses no_cache sometimes. If you set no_cache as preVar, it will be encoded in URLs and Google (or other search engine) may index this URL (with no_cache) and without no_cache. Thus it may result in two different URLs with the same content.

Google have strict policies on content spam and these policies become more and more strict. Currently it is not even good to have www and non-www versions of the site because they are seen as distinct sites but with the same content (Google Sitemaps can solve this though) and can be treated as spam. But links with no_cache and without it on the same site can damage site ratings even more.

Thus, when you read manuals and study examples, think twice: do you really want to copy this code to your configuration. You must understand: examples are not always good for real life. They are examples, not solutions!

And do not use no_cache in preVars. It is better if it works as normal parameter to URL. This is how it is supposed to work.