my c# code not accepting rotate style

Jul 27 2016 2:10 AM

watermarkContent = "Viewed by " + dsUserDetails.Tables[0].Rows[0]["ContactFirstName"].ToString() + " " + dsUserDetails.Tables[0].Rows[0]["ContactLastName"].ToString() + " " + dsUserDetails.Tables[0].Rows[0]["OrgTimeZone"].ToString();

strBody.Append("<span style='transform: rotate(-90deg);color: #7a7a7c;font-size: 13px;font-family: Arial;line-height: 30px;margin:0 15px 0 0;padding:0;'>" + watermarkContent + "");