Дмитрий

function changeCss() {
		document.getElementById("styleBright").href="css/style.css";
		document.getElementById("switcher").value="Back to default";
		document.getElementById("switcher").onclick = changeCssToDefault;
	}
	
	function changeCssToDefault() {
		document.getElementById("styleBright").href="css/main.css";
		document.getElementById("switcher").value="Switch the light";
		document.getElementById("switcher").onclick = changeCss;
	}