W3 Total Cache Fixed Error

It means that when W3TC went to open the advanced-cache.php file (located in /wp-content) it noticed that the file was not created by W3TC but is/was in fact done by a different cache plugin … meaning you have an existing cache program still running when u attempted to activate w3tc. You are best advised to disable the OTHER cache plugin you are using which by doing should remove that advanced-cache.php file, and then activate W3TC which will then create its own advanced-cache.php.