This javascript cut & paste code snippot not only allows the viewer to designate the background color. This nifty code snippet also stores a cookie and remembers the viewers preferences made and recall them on the visitors return visit.

Change background color

Insert this code into your HEAD of HTML

<!-- // == This Script Free To Use Providing This Notice Remains == // // == This Script Has Been In The http://www.DesignerWiz.com Javascript Public Archive Library == // // == NOTICE: Though This Material May Have Been In A Public Depository, Certain Author Copyright Restrictions May Apply == // --><SCRIPT LANGUAGE = "JavaScript"> <!-- Original: Mattias Sjoberg <!-- Begin var expDays = 30; //days before cookie expires var exp = new Date(); exp.setTime(exp.getTime() + (expDays*24*60*60*1000)); function color(){ var favColor = GetCookie('color'); if (favColor == null) { favColor = prompt("What is your favorite background color?"); //message delivered in popup SetCookie('color', favColor, exp); } document.bgColor=favColor; return favColor; } function set(){ favColor = prompt("What is your favorite background color?"); //message delivered in popup SetCookie ('color', favColor, exp); } function getCookieVal (offset) { var endstr = document.cookie.indexOf (";", offset); if (endstr == -1) endstr = document.cookie.length; return unescape(document.cookie.substring(offset, endstr)); } function GetCookie (name) { var arg = name + "="; var alen = arg.length; var clen = document.cookie.length; var i = 0; while (i < clen) { var j = i + alen; if (document.cookie.substring(i, j) == arg) return getCookieVal (j); i = document.cookie.indexOf(" ", i) + 1; if (i == 0) break; } return null; } function SetCookie (name, value) { var argv = SetCookie.arguments; var argc = SetCookie.arguments.length; var expires = (argc > 2) ? argv[2] : null; var path = (argc > 3) ? argv[3] : null; var domain = (argc > 4) ? argv[4] : null; var secure = (argc > 5) ? argv[5] : false; document.cookie = name + "=" + escape (value) + ((expires == null) ? "" : ("; expires=" + expires.toGMTString())) + ((path == null) ? "" : ("; path=" + path)) + ((domain == null) ? "" : ("; domain=" + domain)) + ((secure == true) ? "; secure" : ""); } function DeleteCookie (name) { var exp = new Date(); exp.setTime (exp.getTime() - 1); var cval = GetCookie (name); document.cookie = name + "=" + cval + "; expires=" + exp.toGMTString(); } // End --> </script>

Insert this code into your BODY section

<p align="center"><!-- Demonstration --> <script language="JavaScript" type="text/javascript"> document.write('your favorite background color is : ' + color()); </script> <br><a href="JavaScript:set()">Change background color</a></p>

Simply Cut and Paste Script code
Be sure to properly place script position in HEAD of html 

This script has been in the DesignerWiz.com Public Library.