positioning elements inside a div

I am struggling with correctly positioning 4 elements inside a div using CSS. The solution may include slight changes to the markup, so consider the following example XHTML

<div id="enter_exit_buttons">
<p id="enter_button"><a href="mainpage.html"><img src="images/enterbutton.jpg"
alt="enterbutton.jpg" /></a></p>
<p id="exit_button"><a href="http://www.gottago.com"><img src="images/exit.jpg"
alt="exit_button" /></a></p>
<p>Website Template By: some name you can't see</p>

<p>Copyright © 2007 awebpage.com.com || All Rights Reserved.</p>
</div>

At present, there are no existing rules in the CSS file for #enter_exit_buttons or it's contents. The div above the enter_exit_buttons div has a padding-bottom: 30px; rule in place so I have some room "over my head" so to speak.

What I need is for the first two elements (enter_button, and exit_button) to be centered on one line seperated by 30 or so px. The last two elements also need to be centered, each on it's own line.

One XHTML book, and next to zero experience with CSS is not getting good results. Some help would be appreciated.

Thanks