functon enter()
{
  if (username!=null && username!="" && password!=null && password!="")
    {
    setCookie('username',username,1,'password',password);
     logou
    }
}
function setCookie(c_name,value,expiredays,c_name2,value2)
{
var exdate=new Date();
exdate.setDate(exdate.getDate()+expiredays);
document.cookie=c_name+ "=" +escape(value)+
document.cookie=c_name2+ "=" +escape(value2)+
((expiredays==null) ? "" : ";expires="+exdate.toGMTString());
}

function getCookie(c_name)
{
if (document.cookie.length>0)
  {
  c_start=document.cookie.indexOf(c_name + "=");
  if (c_start!=-1)
    {
    c_start=c_start + c_name.length+1;
    c_end=document.cookie.indexOf(";",c_start);
    if (c_end==-1) c_end=document.cookie.length;
    return unescape(document.cookie.substring(c_start,c_end));
    }
  }
return "";
}
function checkCookie()
{
username=getCookie('username');
password = getCookie('password')
if (username!=null && username!="" && logout!==true)
  {
  alert('Welcome again '+username+'!');
  }
else if (username!= null && username!="" && logout!==false)
  {
  alert("You must sign in!")
  }
  else
  alert("You must sign up!")
 <input type="password" id="password1" value="" />
 <input type="password" id="username1" value="" />
 <input type="button" id="button1" onclick="enter()"
  }
}