SO fiddle
Test Fiddle mainly for SO Questions
by Nick Craver
HTML
<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.4/themes/overcast/jquery-ui.css">
JavaScript
var msg = {"error":["The Firstname field is required.","The Lastname field is required.","The Address 1 field is required.","The City field is required.","The Zipcode field is required.","The Receive Mailing List field is required."]};
alert(msg.error.join('\n'));