// store screen width in a cookie so that the best size for the gallery page can be 
// calculated in dispgallery.php
var data = screen.width;
var expDate = getExpDate(180,0,0);
setCookie("screenwidth",data,expDate);

// utility function to retrieve a future expiration date in proper format;
// pass three integer parameters for the number of days, hours,
// and minutes from now you want the cookie to expire; all three
// parameters required, so use zeros where appropriate
function getExpDate(days, hours, minutes) {
    var expDate = new Date();
    if (typeof days == "number" && typeof hours == "number" && typeof hours == "number") {
        expDate.setDate(expDate.getDate() + parseInt(days));
        expDate.setHours(expDate.getHours() + parseInt(hours));
        expDate.setMinutes(expDate.getMinutes() + parseInt(minutes));
        return expDate.toGMTString();
    }
}

// store cookie value with optional details as needed
function setCookie(name, value, expires, path, domain, secure) {
    document.cookie = name + "=" + escape (value) +
        ((expires) ? "; expires=" + expires : "") +
        ((path) ? "; path=" + path : "") +
        ((domain) ? "; domain=" + domain : "") +
        ((secure) ? "; secure" : "");
}