How to know any website is created on which technology?

http://builtwith.com/

How to know the IP address of any website?

http://en.utrace.de/

How to know the hosting domain of any website?

http://www.whoishostingthis.com/

Removing double/ multiple comma from a string in c#

Use namespace:
using System.Text.RegularExpressions;

then do the following code:

string inputString = "'\"1\":\"C\",\"2\":\"A\",\"3\":\"C\",,\"5\":\"C\",\"6\":\"B\",,\"8\":\"C\",,\"10\":\"C\",'";
string outputString = Regex.Replace(inputString, ",{2,}", ",").Trim(',');