User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv:1.9b5) Gecko/2008032620 Firefox/3.0b5 Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv:1.9b5) Gecko/2008032620 Firefox/3.0b5 The following code raises an error when run locally (file: protocol). new XMLHttpRequest().open('GET', 'anyfile'); I do not think this was the case in FF3b4. The error I get in Firebug (German "Die Erlaubnis für den Aufruf der Methode XMLHttpRequest.open wurde verweigert" This should translate to: "Permission denied to call mathod XMLHttpRequest.open" Reproducible: Always Steps to Reproduce: 1. run new XMLHttpRequest().open('GET' /*anything*/, 'anyfile' /*at least one char*/); locally. Actual Results: error Expected Results: no error

You can not link from remote (http://) to local files. You can only access local files in the same directory if you want to open a local file form a document also loaded via file://.

Actually, that is exactly what I meant. The document is run locally, the adress bar shows the file:// protocol, but I can not access anything within the same directory oder in sub-directories via xhr.

As described in comment 2 it should work (source a local file:, XHR target a local file in the same or sub directory). This is a duplicate of bug 425201 and has been fixed in nightly test builds for a couple of weeks.