The old and many times both missused and missinterpreted
html-standards have been made obsolete by the XML-based xhtml
standards for document structuring that are used together with the CSS
standards for document appearance and rendering specification.  Most
modern browsers are capable of handling these new standards, however
there are some exceptions.  For example MicroSoft Internet Explorer is
known to not fully support these standards and does not acknowledge
the mime-type for the new xhtml standards.  Therefore users of this
browser, and other browsers like it, can experience that some pages
are rendered wrongly and other pages won't render at all.  It will try
to save pages that use the correct mime-type to file rather than
display them in the browser.