Inadvertently erased some code

I have a WordPress website which has the academy theme. Today I have gone into the same options and under the styling option there is a box which says custom CSS. This is now blank and I am sure there was some text in it before. As a consequence on my homepage where I have a slider, I originally had a display box which had text in it and which changed with the background image. Now only the text remains. Please can somebody tell me how to reinstate the original box. My website address is http://www.homestayenglish.uk.com. Any help would be appreciated