I am trying to create a login/register page, i would like it so when the user presses th 'register now' button on the home page, a popup in the same website appears but the back is transparent and dull, here is an example of what i mean as i don't know how to explain it, 

<http://www.crazely.com/graphic/login-page-design-samples-ui-and-cool-stuff/>

also what i found on this page,

<http://www.pmob.co.uk/temp/javascript-centre.htm>

Basically i would just like to know how to do this, 

If possible i would like to keep away from javascript or j query as much as possible 
Thankyou for your help