Thanks, Captain Obvious. My topic title is "Ajax Plugin - server side setup", so I'm well aware it's not a C2 specific issue.
I was merely posting incase anyone else had encountered this issue and had a simple solution. Your response of posting a link to search engine results doesn't help anything. It's an immature dig suggesting I was being lazy by enquiring here. I wasn't looking for a quick fix, I was looking for help from someone experiencing an AJAX related issue within a C2 environment.
I am more than capable of pasting my error message into the search engine. I did indeed do that, but as I have no knowledge of web programming/scripting etc it all means nothing.
If this forum was full of smart arses like yourself it'd make for a very difficult place to ask for help.
And in the spirit of what this forum should be about, I have the solution for anyone else who may encounter this problem. For me, I had to add the following to a file named ".htaccess"
Header add Access-Control-Allow-Origin "*"
Header add Access-Control-Allow-Headers "origin, x-requested-with, content-type"
Header add Access-Control-Allow-Methods "PUT, GET, POST, DELETE, OPTIONS"