When I request a particular web page, the browser first tries to load the page from its cache, rather than submitting a new HTTP request.

If I use a php url I wil use something like this

myRequest.open("GET", url  + myRandom, true);
or I use the current timestamp
myRand= + new Date().getTime();
But the problem is I parse with java scripts text and xml files(url) not php and the trick above is not working with this kind of file.
I can add HTTP headers to the data returned by server-side routines, intended to tell the browser not to cache a particular page,but different browsers have different cache support different header declarations, making it difficult to ensure that pages are not cached.
What I can do in this situation ?