var divs = new Array ("action-interior1","action-interior2");

function hideDivs() {
	for (var i=0; i<divs.length; i++)
	document.getElementById(divs[i]).style.display = 'none';
}

function showDiv() {
	hideDivs(); //hide them all before we show the next one.
	var randomDiv = divs[Math.floor(Math.random()*divs.length)];
	var div = document.getElementById(randomDiv).style.display = 'block';

	setTimeout(showDiv,3000); //set a delay before showing the next div
}

showDiv();