Last week I've costumize the website which use popup. This using CSS. insert before<head>: <script type="text/javascript" src="js/popup.js"></script> PHP: Insert this to your body : <div id="blanket" style="display:none;"></div> <div id="popUpDiv" style="display:none;"> <a href="#" onclick="popup('popUpDiv')">close</a> <p>your content</p> </div><a href="#" onclick="popup('popUpDiv')">click popup</a> PHP: CSS code: /*Popup*/#blanket { background-color:#111; opacity: 0.65; position:absolute; z-index: 9001; /*ooveeerrrr nine thoussaaaannnd*/ top:0px; left:0px; width:100%; -webkit-border-radius: 0.5em; -moz-border-radius: 0.5em; border-radius top:50px; left:200px; box-shadow: 0 0 10px #222; -webkit-box-shadow: 0 0 10px #222; -moz-box-shadow: 0 0 10px #222;}#popUpDiv { position: fixed; background-color:#eeeeee; width:300px; height:250px; top:150px; left:450px; z-index: 800; /*ooveeerrrr nine thoussaaaannnd*/ -webkit-border-radius: 0.5em; -moz-border-radius: 0.5em; border-radius box-shadow: 0 0 8px #222; -webkit-box-shadow: 0 0 8px #222; -moz-box-shadow: 0 0 8px #222; } PHP: Save Java Script file name : popup.js, function toggle(div_id) { var el = document.getElementById(div_id); if ( el.style.display == 'none' ) { el.style.display = 'block';} else {el.style.display = 'none';}}function blanket_size(popUpDivVar) { if (typeof window.innerWidth != 'undefined') { viewportheight = window.innerHeight; } else { viewportheight = document.documentElement.clientHeight; } if ((viewportheight > document.body.parentNode.scrollHeight) && (viewportheight > document.body.parentNode.clientHeight)) { blanket_height = viewportheight; } else { if (document.body.parentNode.clientHeight > document.body.parentNode.scrollHeight) { blanket_height = document.body.parentNode.clientHeight; } else { blanket_height = document.body.parentNode.scrollHeight; } } var blanket = document.getElementById('blanket'); blanket.style.height = blanket_height + 'px'; var popUpDiv = document.getElementById(popUpDivVar); popUpDiv_height=blanket_height/2-150;//150 is half popup's height popUpDiv.style.top = popUpDiv_height + 'px';}function window_pos(popUpDivVar) { if (typeof window.innerWidth != 'undefined') { viewportwidth = window.innerHeight; } else { viewportwidth = document.documentElement.clientHeight; } if ((viewportwidth > document.body.parentNode.scrollWidth) && (viewportwidth > document.body.parentNode.clientWidth)) { window_width = viewportwidth; } else { if (document.body.parentNode.clientWidth > document.body.parentNode.scrollWidth) { window_width = document.body.parentNode.clientWidth; } else { window_width = document.body.parentNode.scrollWidth; } } var popUpDiv = document.getElementById(popUpDivVar); window_width=window_width/2-150;//150 is half popup's width popUpDiv.style.left = window_width + 'px';}function popup(windowname) {toggle('blanket');toggle(windowname);} PHP: