Lost image in section box

I'm an educator, not a web person. So most of what I read here is in a foreign language. While working in Omeka, I encountered an error. Didn't think to write it down. Then the image and text in one of the section buttons disappeared. Can you tell me how to get the image back in everyday language?

Hi,

We are going to need to know more information so that we can help you figure out what went wrong.

1. Can you reproduce the error and post it for us?
If we don't know what error you received, we cannot isolate the problem.

2. Can you tell us exactly what steps you were following when you encountered this error? Were you adding an item to your archive, were you creating an exhibit, exhibit page?

3. Can you provide us with a link to the problematic page?

Thanks,
Sheila

I don't know how to reproduce the error--sorry! We have downsized at work and have a skeleton staff, so I'm learning by reading instructions on this site and trial & error (mostly error). I think I was either adding an item to the archive or pulling an item image into a page. Here is a link to the page. The problem box is second from the left.
http://plainsart.org/learnonline/exhibits/show/david-bradley Thanks!

Your missing box looks like it's not related to anything from Omeka, it's a problem in your CSS stylesheet.

The markup on the page for that box has an id of 'chippewa-family', but your stylesheet refers to 'chippewafamily' (no hyphen).

The easiest way to fix this is to replace 'chippewafamily' with 'chippewa-family' on line 68 your stylesheet, which should be located at themes/bradley-exhibit/css/screen.css.

I probably did something wrong with the address because it came up "page not found." But I took out the hyphen in the slug for the Chippewa Family section and that did the trick. I remember now putting the hyphen in yesterday to be consistent with other pages I've created. Lesson learned!
THANKS!