I know this is a common question but have been looking for hours and I can't seem to find one that is for a background image to refresh on reload that is in a table using a class (not in an ID) - I should have built the whole site in css but i'm not that good at it yet!

this is where i want the image to go

<td class="happen">

in this page

http://www.23rdandunion.org/happen.htm

this is my css

td.happen {background-image:url(../images/happen.jpg); background-repeat:no-repeat; height:566px;}

Change the class each time, and style each class differently.
It's easier to do this from the server, but if you have a static site, you can change the class name with JavaScript by selecting the TD as a DOM object then changing its className property. Of course, you'll want to do it randomly, which requires the Math.random() method.