$.getJSON() works in IE9, but not in Chrome and FireFox, whats wrong in my code?

You can use the built in error function to display the error and debug it.

$(document).ready(function(){ // Make sure your jQuery is inside this$.getJSON("sample.json", function(data) {    alert('Point 1 Reached.');    console.log(data); // Here we log to our console    $.each(data.feed.entry, function(i, item) {             // Do your stuff here        }); // End of $.each// Here Success, Completed & Error do something. chained onto $.getJSON        }).success(function() { alert("success"); })          .error(function(jqXHR, textStatus, errorThrown) { // Debug the error!!                    console.log("error " + textStatus);                    console.log("error throw " + errorThrown);                    console.log("incoming Text " + jqXHR.responseText);                }) // End of .error          .complete(function() { alert("complete"); });        });}); // End of DOM Ready

This should show you the error in the console window of firefox or chrome (console.log will not work in IE and break the script). To bring up the console window in firefox or chrome press F12. If the JSON is not working, it will show an error which you can debug.

Update
Also make sure that this code is in your $(document).ready(). The $.getJSON() might cause unexpected behaviours across browsers if using it otherways.

Is this running on a web server or are you just opening the file in a browser? If you are just opening the file you will have problems.