// source => FB: Simple Javascript
function ready(callback){
 	// in case the document is already rendered
    if(document.readyState != 'loading') callback();

    // modern browsers
    else if(document.addEventListener)
    	document.addEventListener('DOMContentLoaded', callback);
    // IE < 8
    else document.attachEvent('onreadystatechange', function(){
    	if(document.readyState == 'complete') callback();
    });
}

ready(function(){
	// do something
}