<form  onsubmit="return confirm_action('Really delete?')" action="" method="post" accept-charset="utf-8">

function confirm_action(message) {
    if(message===undefined){message='are you sure?';}

    if(confirm(message)){
        // prevents clicking the submit button more than once
        prevent_double_submit.call(this);
        return true;
    }
    else{
        return false;
    }
}

function prevent_double_submit(){
    $('input[type=submit]',this).attr('disabled', 'disabled');
    $('input[type=submit]',this).attr('style', 'background:url(/files/images/colorbox/loading.gif) no-repeat center');
}