var slider = {
    currentDivNum:0,
    contentDivs:0,
    init:function(parentDiv,className){
	    var divs=document.getElementById(parentDiv).getElementsByTagName("div")
	    contentDivs = []
	    currentDivNum = 0;
	    for (var i=0; i<divs.length; i++){
            if(divs[i].className == className)
            {
               contentDivs.push(divs[i])
            }
	    }
	    if(contentDivs.length>0){
	        for (var i=1; i<contentDivs.length; i++){
	        	 contentDivs[i].style.display='none'
	        }
	    }
	    delete init;
    },
    next:function(){
        var num = currentDivNum+1
        if(num == contentDivs.length)
        {
            num = 0;
        }
        this.change(num);
    },
    previous:function(){
        var num = currentDivNum-1
        if(num == -1)
        {
            num = contentDivs.length -1;
        }
        this.change(num);
    },
    change:function(newNum){
    	contentDivs[currentDivNum].style.display='none';
    	contentDivs[newNum].style.display='block';
		currentDivNum = newNum
    }
 }