The OP is using HTML, not XHTML (they said "HTML" and XHTML doesn't have an INPUT element (it does have an input element though)).

So the element is already closed and adding a "/" will effectively make it mean <INPUT type="image" name="page" value="1">> thanks to SGML rules that most browsers don't implement (Appendix C of XHTML 1.0 exploits this common browser bug).