Background color for caution blocks in the Handbook

[Manolis Kiagias]

On 03/05/2011 08:11 PM, Glen Barber wrote:
>
> I was originally hesitant to use yellow to avoid causing visual pain
> when reading.  How about the colors I have here:
>
> http://www.glenbarber.us/FreeBSD/doc/en_US.ISO8859-1/books/handbook/disks-hast.html
>
>   

I think it looks fine. It is a lighter version of the warning color,
which makes sense.
Commit it before it gets into a bikeshed :)