title: how to position a div in the center and hide it?
body: <p>i want to make a login page but it is hidden in the center of the main page.</p>
  
  <p>and then i use jquery to make the div that surrounds it visible and it will be like the login page at www.bytes.com.</p>
  
  <p>but i cant figure it out how to center it with css. it doesnt work without affecting the main pages div positions.</p>
  
  <p>i just want it to float over the main page. someone?</p>