From @Kevin B's comment "If you make a GET request in IE8 and then later make a POST request to the same URL, IE8 will incorrectly return the cached response rather than doing the POST."
$.ajax({
type: "GET",
url: "test1.htm"
});
/* In IE8 this comes from the cache */
$.ajax({
type: "POST",
url: "test1.htm"
});
$.ajax({
type: "GET",
url: "test2.htm",
cache: false // adds a timestamp to the querystring
});
/* Even IE8 avoids the cache */
$.ajax({
type: "POST",
url: "test2.htm"
});