This one is easy
You have a redirect set to forward to another domain. It is set to keep the same address in the address bar.
This is not a hack or an exploit, it is something set on your end usually called stealth redirection.
See your source code
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN" "http://www.w3.org/TR/html4/frameset.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Π.Α.Σ.Π. ΟΡΕΣΤΙΑΔΑΣ</title>
<meta name="description" content="">
<meta name="keywords" content="">
</head>
<frameset row="*" frameborder="NO" border="0" framespacing="0">
<frame src="http://www.potouridis.com/pasp-orestiadas/" name="siteFrame">
</frameset>
<noframes>
<body>
</body></noframes>
</html>
I use this all the time, totally harmless and working the way its supposed to be