var expDays = 300;
var exp = new Date(); 
exp.setTime(exp.getTime() + (expDays*24*60*60*1000));

function set() {
    favColor = prompt("What is your favorite background color?");
    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,j;  
    while (i < clen) {    
	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();
}