I've been actively using the protocol-less URLs for pretty much all external content lately and everything has been working great. I recently decided to start getting alerts for all 404s from my server and sudden was flooded with errors that had to do with linking to external content with "//".
$_SERVER output shows:
["REDIRECT_URL"]=>
string(46) "/www.googleadservices.com/pagead/conversion.js"
["GATEWAY_INTERFACE"]=>
string(7) "CGI/1.1"
["SERVER_PROTOCOL"]=>
string(8) "HTTP/1.1"
["REQUEST_METHOD"]=>
string(3) "GET"
["QUERY_STRING"]=>
string(0) ""
["REQUEST_URI"]=>
string(47) "//www.googleadservices.com/pagead/conversion.js"
["SCRIPT_NAME"]=>
string(10) "/index.php"
["PHP_SELF"]=>
string(10) "/index.php"
["REQUEST_TIME"]=>
int(1373437449)
I'm running Zend Framework MVC, so everything is supposed to be routed to index.php for processing, but external stuff loads just fine. Going to pages with these links throws no errors via firebug, but I'm getting flooded with errors when it redirects to the single slash "REDIRECT_URL" as seen above.
This means that: //www.googleadservices.com/pagead/conversion.js
gets redirected to: /www.googleadservices.com/pagead/conversion.js
which really means: http://www.mydomain.com/www.googleadservices.com/pagead/conversion.js which turns into an error: Exception information - Message Invalid controller specified (www.googleadservices.com)
Since the site works and there really isn't any actual visible problems, I'm just curious why this would be happening in the background and was curious if anyone else has ever seen such a thing.