disable submit on first click

/*
 Disable HTML form submit button on first click to prevent double clicks
 following code into <head> section of your page
*/

<script language="javascript" type="text/javascript">
function dis(){
frm=document.forms[0];
frm.submit.disabled=true;
}
</script>

// and the following code into <form> section :
onsubmit="dis();"

/*
 example
<form method="post" action="/index.php" onsubmit="dis();">
*/