“REST” style AJAX calls can be cached by the browser if the server is not properly configured. For some services this is a good thing (think, a mapping service), but often it is a hassle.

The way I see it there are 3 ways to get around it:

• The “proper” way is to configure the caching on the server app. For example in ASP.NET use Response.Cache.SetCacheability(HttpCacheability.NoCache), or use the <%@ OutputCache %> tag.
• The “fix it from the client” way is to add a random parameter to the Javascript. This way the query is different every time. If the server can accept POST as well as GET you can also use a POST since those are not cached.
• The “lazy” way is to force a header from the server configuration. In IIS this is super easy:
  1. edit the properties of the directory that contains your script services
  2. go to HTTP Headers
  3. Add a custom header: name is “Cache-Control” and value is “no-cache”

Lots of conflicting information on this one… Most pages will recommend using

netscape.security.PrivilegeManage.enablePrivilege("UniversalBrowserRead");
netscape.security.PrivilegeManage.enablePrivilege("UniversalBrowserRead");

Or go to about:config and toggle the setting for signed.applets.codebase_principal_support.
This didn’t do the trick for me, in fact it appears it is NOT required when you want to debug local files.
The only thing I had to do was create a file user.js under the FF profile directory (\D&S\user\App Data\Mozilla etc) with following content:

user_pref("capability.policy.XMLHttpRequestToAnySite.XMLHttpRequest.open", "allAccess");
user_pref("capability.policy.XMLHttpRequestToAnySite.sites", "http://localhost");
user_pref("capability.policy.XMLHttpRequestToAnySite.sites", "file://");
user_pref("capability.policy.policynames", "XMLHttpRequestToAnySite");

There is a security implication though. Any HTML file open from the hard drive will be able to communicate with any web site. Unfortunately I was not able to restrict the “file://” URL to a specific directory (like “file:///E:/html_projects” or something like that). Because of that I may have to keep coming back to this file and turn it off when I am done debugging. Or debug from the localhost server.