Untitled

<html>
<head>
<script language="JavaScript">
   <!--
   function teste() {
      if (document.upload.arquivo.value=="") {
         alert("Arquivo para upload não informado!")
         document.upload.arquivo.focus()
         return false
      }
   }
   //-->
</script>
</head>
<body>
   <h2>Upload Simples</h2><br>
   <form name="upload" action="upload.php" method="post" enctype="multipart/form-data" onsubmit="return teste()">
      <input type="file" name="arquivo" size="60">
      <br>
      <input type="submit" name="enviar" value="Upload!">
   </form>
</body>
</html>