function ajax_change_page(_page, _lang, _category)
{

	  $.extend($.blockUI.defaults.overlayCSS, { backgroundColor: '#000000', opacity: '0.5' });
    $.blockUI('<img src="images/loading.gif" vspace="10">');
		
		if (_category == undefined) {
			_category = '';
		}
		
    // get contents for this page 
    if (_page) {
    	$.get('portfolio.html', {ajax: 1, page : _page, category : _category, lang: _lang}, function(data) {
    		data = eval( '(' + data + ')' );
				
				if (data["error"] == "0") {
					$.unblockUI();
					$("#gallery").html(data["Response"]);
				} else {
					$.unblockUI();
				}    		
    		
    		});    	    	
    }	
}