When downloading files from Web servers like IIS or Tomcat via binary streams (for example, by setting the Header to "Content-disposition:inline"), if the file being downloaded has an Office 2007 extension such as dotx, docx, or pot, the icon in the download dialog box will change to that of a ZIP file, and the corresponding filename will also have its extension changed to .zip. This situation arises because of how Internet Explorer determines the type of downloaded files. If it cannot find the corresponding MIME type for the given file extension, IE will automatically determine the file type based on the data stream. Microsoft implemented a completely different handling method for Office 2007 formats, which is why this issue occurs.