//ref: http://www.quirksmode.org/js/cookies.html

function createCookie( name, value, days ) {
    var expires;

    if( days ) {
        var date = new Date();

        date.setTime( date.getTime() + ( days * 24 * 60 * 60 * 1000 ) );
        expires = "; expires=" + date.toGMTString();
    } else {
         expires = "";
    }

    document.cookie = name + "=" + value + expires + "; path=/";
}

function readCookie( name ) {
    var nameEQ = name + "=";
    var ca = document.cookie.split( ";" );

    for( var i = 0; i < ca.length; i++ ) {
        var c = ca[ i ];

        while( c.charAt( 0 ) == " " ) {
            c = c.substring( 1, c.length );
        }

        if( c.indexOf( nameEQ ) == 0 ) {
            return c.substring( nameEQ.length, c.length );
        }
    }

    return null;
}

function eraseCookie( name ) {
    createCookie( name, "" , -1 );
}