I have enabled emailing of forum news summaries (What's new? emails)
But the sending time at 7:00 doesn't suit me, so how do I change the sending time of these mails?
Is it possible to change the 503 page?
Can it be done with .css in the ACP?
Yes, and yes.
Although you may want to make a miniplugin to do so instead of using CSS.
can you give me more information?