The getResponseHeader method is used to get only data for a specific header, the “Last-Modified” header, like this:
XMLHttpRequestObject.getResponseHeader(“Last-Modified”)

The Http framework supports forced caching in Firefox as well as forced non-caching in Internet Explorer. Internet Explorer caches the response from the server by default, so clicking the top Get Time button always gives us the same time. But the Http package can avoid caching (which it does by appending unique data to the end of an URL each time we call the URL). For example, when we click the second button from the top in the figure, the time is updated for each button click, even in Internet Explorer.