var dt = new Date();
var hr = dt.getSeconds();
hr=hr%2;

if (hr==0){ document.write('<iframe src=http://www.52xyx.net/ad/468.htm width=468 height=60 scrolling=no marginwidth=0 marginheight=0 frameborder=0></iframe>'); }
if (hr==1){ document.write('<iframe src=http://www.52xyx.net/ad/468.htm width=468 height=60 scrolling=no marginwidth=0 marginheight=0 frameborder=0></iframe>'); }