Facebook Sign In Button

<script language="javascript" type="text/javascript">
    // Load the SDK Asynchronously
    (function (d) {
        var js, id = 'facebook-jssdk', ref = d.getElementsByTagName('script')[0];
        if (d.getElementById(id)) { return; }
        js = d.createElement('script'); js.id = id; js.async = true;
        js.src = "//connect.facebook.net/en_US/all.js";
        ref.parentNode.insertBefore(js, ref);
    } (document));

    // Init the SDK upon load
    window.fbAsyncInit = function () {
        FB.init({
            appId: '680827721940158', // Write your own application id
            channelUrl: '//' + window.location.hostname + '/channel', // Path to your Channel File
            scope: 'id,name,gender,user_birthday,email,user_location,user_hometown',
            status: true, // check login status
            cookie: true, // enable cookies to allow the server to access the session
            xfbml: true  // parse XFBML
            //,perms: 'user_address, user_mobile_phone'
        });
       

        // listen for and handle auth.statusChange events
        FB.Event.subscribe('auth.statusChange', function (response) {
            if (response.authResponse) {
                // user has auth'd your app and is logged into Facebook
                var uid = "http://graph.facebook.com/" + response.authResponse.userID + "/picture";
                FB.api('/me', function (me) {
                    if (me.name) {
                        //me.name
                        document.getElementById('<%= txtNewFirstName.ClientID%>').value = me.first_name;
                        document.getElementById('<%= txtNewLastName.ClientID%>').value = me.last_name;
                        document.getElementById('<%= txtNewEmail.ClientID%>').value = me.email;

                        var location = me.location.name.split(',');

                        //For Country DropDown
                        var isCountry = false;
                        $("#<%=ddlNewCountry.ClientID%> option[selected]").removeAttr("selected");
                        var textToFind = location[1].trim();

                       me.languages[0].name.trim();
                       // $("#<%=ddlNewCountry.ClientID%>").val(location[1].trim());
                        //me.birthday;
                        // uid;
                        //me.gender;
                    }
                })
                document.getElementById('auth-loggedout').style.display = 'block';
                document.getElementById('auth-loggedin').style.display = 'block';
            } else {
                // user has not auth'd your app, or is not logged into Facebook
                document.getElementById('auth-loggedout').style.display = 'block';
                document.getElementById('auth-loggedin').style.display = 'none';
            }
        });
        $("#auth-logoutlink").click(function () { FB.logout(function () { window.location.reload(); }); });
    }
</script>

Create account in
http://developers.facebook.com/
create new application and please the url in web login(where to use)
Make sure that sandbox is disable.