Download attribute dosent download some files

This bug is publicly visible.

User Agent: Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:15.0) Gecko/20100101 Firefox/15.0 Build ID: 20120825192214 Steps to reproduce: added the attribute download="myfilename.txt" to a hyperlink tag clicked the hyperlink Actual results: Firefox will open the file locally (in the case of an image or other known file type) or it will offer to download the file with a randomly generated filename. Expected results: Firefox should always offer to download the file using "myfilename.txt" as default file name to the downloaded file as mentioned in the MDN documentation - download HTML5 This attribute, if present, indicates that the author intends the hyperlink to be used for downloading a resource. If the attribute has a value, the browser should interpret that as the default filename that the author recommends for use in labeling the resource in a local file system. There are no restrictions on allowed values, but you should consider that most file systems have limitations with regard to what punctuation is supported in file names, and browsers are likely to adjust file names accordingly. Note: You can use this with data:, blob: and filesystem: URLs, to make it easy for users to download programmatically generated content.