I've been reading about Access-Control-Allow-Origin because it seems effective at allowing cross domain requests since I have access to the external site. My question ism how do I use Access-Control-Allow-Origin to allow cross domain requests. I tried this (don't laugh) (by the way all I want is for a single number, 1 or 0 to be returned)
<html>
<head>
Access-Control-Allow-Origin: *
</head>
<body>
1
</body>
</html>
Am I close? Thanks for your help. If there is an easier way to do a simple cross-domain request let me know.
That is an HTTP header. You would configure your webserver or webapp to send this header ideally. Perhaps in htaccess or PHP.
Alternatively you might be able to use
<head>...<meta http-equiv="Access-Control-Allow-Origin" content="*">...</head>
I do not know if that would work. Not all HTTP headers can be configured directly in the HTML.
This works as an alternative to many HTTP headers, but see @EricLaw's comment below. This particular header is different.
Caveat
This answer is strictly about how to set headers. I do not know anything about allowing cross domain requests.
About HTTP Headers
Every request and response has headers. The browser sends this to the webserver
GET /index.htm HTTP/1.1
Then the headers
Host: www.example.com
User-Agent: (Browser/OS name and version information)
.. Additional headers indicating supported compression types and content types and other info
Then the server sends a response
Content-type: text/html
Content-length: (number of bytes in file (optional))
Date: (server clock)
Server: (Webserver name and version information)
Additional headers can be configured for example Cache-Control, it all depends on your language (PHP, CGI, Java, htaccess) and webserver (Apache, etc).