<!DOCTYPE html>
<html>
<head>
</head>
<body onload="set_bk_color()">
<form id="aaa_id">
<input type="button" onclick="alert(document.forms[0].id);" value="aaa form" />
</form>
<form id="bbb_id">
<input type="button" onclick="alert(document.forms[1].id);" value="bbb form" />
</form>
<form id="ccc_id">
<input type="button" onclick="alert(document.forms[2].id);" value="ccc form" />
</form><script type="text/JavaScript">
function set_bk_color()
{
for (var i = 0; i < document.forms.length; i++)
document.forms[i].style.backgroundColor = 'BLUE';
}
/*
run:
check your browser
*/
</script></body>
</html>