meh, I was bored, asside from the given links, maybe you can do away with this example:
PHP Code:
<html>
<
head>
<
script type="text/javascript">
function 
passMatch(e)
{
    var 
pass e.pass;
    var 
confirmPass e.confirmPass;
    if(
pass.value != confirmPass.value || pass.value == "")
    {
        
alert("Your passwords do not match!");
        
pass.select();
        return 
false;
    }
    else
    {
        return 
true;
    }
}
</
script>
</
head>
<
body>
<
form name="myForm" action="" method="" onsubmit="return passMatch(this);">
Old Password:<input type="password" name="oldPass"><br>
New 
Password:<input type="password" name="pass"><br>
Confirm new Password:<input type="password" name="confirmPass"><br>
<
input type="submit" value="Change password">
</
form>
</
body>
</
html