If when you do with AJAX, you see the error like the figure below, you can follow those step to fix it.

XMLHttpRequest cannot load ... No 'Access-Control-Allow-Origin' header is present on the request resource. Origin ... is therefore not allowed access

ajax cross domain

Step 1: check if mod_headers is enable on Apache

/usr/lib/httpd/modules/ (Linux)
mod headers apache
D:\AppServ\Apache2.2\modules (Windows, ex)
windows mod headers

/etc/httpd/conf/httpd.conf (Linux)
headers_module httpd conf
D:\AppServ\Apache2.2\conf\httpd.conf (Windows, ex)
windows httpd conf

Step 2: Use file .htaccess

<ifModule mod_headers.c>
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"

Upload this file to the working directory.
upload htaccess

Now, you can access cross domain. Check response header at this.

HTTP/1.1 200 OK => 
Date => Sun, 13 Sep 2015 08:18:39 GMT
Server => Apache/2.2.27 (CentOS)
Last-Modified => Sun, 13 Sep 2015 04:02:04 GMT
ETag => "3e40b2-47-51f990301fbc7"
Accept-Ranges => bytes
Content-Length => 71
Access-Control-Allow-Origin => *
Access-Control-Allow-Headers => origin, x-requested-with, content-type
Access-Control-Allow-Methods => PUT, GET, POST, DELETE, OPTIONS
Connection => close
Content-Type => text/plain; charset=UTF-8