Código HTML:
<input onclick="MM_validateForm('theme','','R','preview','','R','nombre','','R');return document.MM_returnValue" name="enviar" type="image" src="upload.gif" border="0" style="cursor:pointer"/>
Código HTML:
<form name="alojar" method="post" action="url/upload.php" style="margin:0px;" enctype="multipart/form-data">
Gracias.