A normal Event Details pop-up looks something like this:
But if you want to slim it down and not show the event's Time and Title or image (after all, they are on the main calendar view) you can make it look like this:
Just paste the following code into the Common Event Information field under Options->Event
<script>jQuery('#event_detail_header').hide()</script>
If you would like to hide only the event description, use the following code in the Common Event Information field instead
<script>jQuery('.event-desc-theme').hide()</script>
Note
This trick will only work for events that were created on the localendar.com website. They will not affect imported events, or events merged from external iCal urls