document.addEventListener('DOMContentLoaded', init);
var first = false;

function init(){
    var elem = document.getElementById('on');
    elem.addEventListener('click',funcon);
	var elem2 = document.getElementById('off');
    elem2.addEventListener('click',funcoff); 
}

function funcon(){
    chrome.tabs.executeScript({
		code: "document.body.style.opacity = '1.0'"
	});
}

function funcoff(){
	chrome.tabs.executeScript({
		code: "document.body.style.MozTransition = 'opacity 1s ease-in'; document.body.style.opacity = '0.0'"
	});
}