protected string GetStyleSheetLink(string url, bool prefixWithImagePath, string prefix, string cacheInvalidationSuffix)
        {
            string realUrl = url;

            if (!realUrl.IsEmpty())
            {
                // i370377 - checks if the theme is external it don't need the local prefix
                if (realUrl.StartsWith("/") || realUrl.StartsWith("http://") || realUrl.StartsWith("https://"))
                {
                    prefixWithImagePath = false;
                }
                if (prefixWithImagePath)
                {
                    realUrl = prefix + realUrl;
                }
                return("    " + CssHelper.GetCssInclude(realUrl + cacheInvalidationSuffix));
            }
            return(null);
        }