The ENCTYPE attribute of the form specifies how the HTTP request should be encoded. All GET requests are submitted as application/x-www-form-urlencoded. The value of multipart/form-data is required (with a POST request) to submit a file to the server. The value of text/plain forces the request to be POST. Windows Internet Explorer 8 and later. In IE8 Standards mode, the enctype Document Object Model (DOM) attribute is now supported and reflects the ENCTYPE content attribute. For more information, see Attribute Differences in Internet Explorer 8. The enctype property was introduced in Internet Explorer 8. If backward compatibility is required, use the encoding property.
Microsoft Developer Network: [Windows Internet Explorer API reference Article]