function show_big2(img)
{
	$(document).ready(function(){
		$('.preloaderimg').css('display', 'block');
		$('#big_img').attr('src', 'http://www.pr-webtech.com/images/portfolio/big/big_'+img+'.jpg').load(function() { 
			$('.preloaderimg').css('display', 'none');
		});
	});
	document.getElementById('big_img').src = 'http://www.pr-webtech.com/images/portfolio/big/big_'+img+'.jpg';
}

function show_big(img)
{
  var obj = img;
  var big_img  = obj.getElementsByTagName('img')[1].src;
  document.getElementById('big_img').src = big_img;
}