function next(deselectTds){
	if(!deselectTds){
		diselectTds();
	}
	if(offset>=thumbnales.length){
		checkButton();
		return;      
	}
	if(offset+ipp>thumbnales.length){
		offset=thumbnales.length-ipp;
	}
	for(i=0;i<ipp;i++){
		document.getElementById("img"+i).src=thumbnales[offset];
		document.getElementById("link"+i).href=urls[offset];
		offset++;
		if(offset>=thumbnales.length){          
			checkButton();
			return;
		}
	}
	checkButton();
}



function prev(){
	diselectTds();
	if(offset<ipp){      
		checkButton();
		return;
	}
	if(offset-ipp*2<0){
		offset=ipp*2;
	}
	offset=offset-ipp*2;
	for(i=0;i<ipp;i++){
		document.getElementById("img"+i).src=thumbnales[offset];      
		document.getElementById("link"+i).href=urls[offset];
		offset++;
	}
	checkButton();
}



function checkButton(){
	if(offset >= thumbnales.length){
		document.getElementById('buttonNext').style.visibility="hidden";
	}
	else
	{
		document.getElementById('buttonNext').style.visibility="visible";
	}
	if(offset<=ipp){
		document.getElementById('buttonPrev').style.visibility="hidden";
	}
	else
	{
		document.getElementById('buttonPrev').style.visibility="visible";
	}  
}



function preloadImages(imgArray){
	for(i=0; i < imgArray.length ;i++){
		img = new Image();
		img.src=imgArray[i];
	}
}



function diselectTds(){
	for(i=0; i<ipp; i++){
		document.getElementById("td_thumbnale_"+i).className="td_thumbnale";
	}
}