Use get;set; as shown below sample:

private static string OverLayText="This is an html"; [Category("Extended Settings"), Personalizable(), WebBrowsable(), WebDisplayName("OverLay text"), WebDescription("OverLay Text")] public string _OverLayText { get { return OverLayText; } set { OverLayText = value; }

    }

Use get;set; as shown below sample:

private static string OverLayText="<b>This is an html</b>";
        [Category("Extended Settings"),
        Personalizable(),
        WebBrowsable(),
        WebDisplayName("OverLay text"),
        WebDescription("OverLay Text")]
        public string _OverLayText
        {
            get
            {
                return OverLayText;
            }
            set
            {
                OverLayText = value;
            }    
        }