Step 44 of (New) Responsive Web Design.
(New) Responsive Web Design - Step 44
The error hint is asking for width, but it means to be asking for the height.
I wrote in a comment in the code where the issue is. The error was noticed when I had accidentally skipped writing the height property. I figure this should be corrected, as it may cause a more modest developer some unnecessary frustration.
Edit: I did a Bing search whether anyone had reported this issue. Bing tends to miss plenty, so if it is an repeat, I do apologise. Also, Step 34 needed a space. It said << div#offwhite-character>> when it meant to say << div >> then <<#offwhite-character>>.