Why this error happens?

<HTML><HEAD>
<style type="text/css">
<!--
.invisible {-moz-opacity: [0];  filter: alpha(opacity=[0]);}
.invisible2 {-moz-opacity: [0]%;  filter: alpha(opacity=[0]);}
-->
</style>

<script>
	var fi
	function enviar(){
		window.document.formup.action="insert.asp"
		window.document.formup.submit();
	}

	function search(){
		fi.click();
	}
	
	function Init(){
		fi=document.getElementById("file");
	}
</script>
<TITLE>Teste</TITLE>
</HEAD>
<BODY leftMargin=[0] topMargin=[0] marginwidth="[0]" marginheight="[0]" onload="Init();">


<form name="formup" method="post" enctype="multipart/form-data" target="_blank">
  <input id="file" type="file" name="fichier" size="[1]">
</form>




<input type="button" name="bt1" size="[1]" value="Send" onclick="enviar();">
<input type="button" name="bt2" size="[1]" value="Select File" onclick="search();">
</body>
</HTML>