Parsing Web Browser Languages can be a pain here are some code snippets we use for getting the actual browser languages

gistfile1.cs

        // Try to match the local date format of the browser 

        var userLanguages = LanguageItem.GetRequestUserLanguages();
        // Ignore if no language preferences
        if (userLanguages != null)
        {
            var culture = CultureInfo.CreateSpecificCulture(userLanguages.First().IsoCode);
            return Updated.ToString("d", culture);
        }
        return Updated.ToString("dd.MM.yyyy");



        /// <summary>
        /// UserLanguages in User Browser Request.
        /// </summary>
        /// <returns>Parsed Browser User Languages ordered by Weight</returns>
        public static IEnumerable<UserLanguage> GetRequestUserLanguages()
        {
            if (HttpContext.Current == null) return null;
            if (HttpContext.Current.Request.UserLanguages == null) return null;

            return HttpContext.Current.Request.UserLanguages.Select(
                        d => new UserLanguage { IsoCode = ParseUserLanguage(d), Weight = ParseUserLanguageWeight(d) }).
                        OrderByDescending(l => l.Weight);
        }

        /// <summary>
        /// Parse the language part of the userlanguage element
        /// </summary>
        /// <example>
        /// E.g. UserLanguages en-US / en;q=0.8 / da;q=0.6 / de;q=0.4 / de-DE;q=0.2 / de-CH;q=0.2
        /// </example>
        /// <param name="s">userLanguage element</param>
        /// <returns>IsoCode</returns>
        private static string ParseUserLanguage(string s)
        {
            return !s.Contains(";q=") ? s : s.Substring(0, s.IndexOf(";q="));
        }

        /// <summary>
        /// Find the weight of the userlanguage 
        /// </summary>
        /// <example>
        /// E.g. UserLanguages en-US / en;q=0.8 / da;q=0.6 / de;q=0.4 / de-DE;q=0.2 / de-CH;q=0.2
        /// </example>
        /// <remarks>comes with a potential ";q=0.8" of none is specified it is assumed as 1 </remarks>
        /// <param name="s">userLanguage element</param>
        /// <returns>the weight / priority from 1 to 0</returns>
        private static double ParseUserLanguageWeight(string s)
        {
            if (!s.Contains(";q="))
            {
                return 10;
            }

            double o;
            var q = s.Substring(s.IndexOf(";q=") + 3);
            return double.TryParse(q, out o) ? o : 10;
        }

        public class UserLanguage
        {
            public string IsoCode
            {
                get; set;
            }

            public double Weight
            {
                get; set;
            }

            #endregion Properties
        }