When starting Apache for the first time, I came across this error message in httpd-error.log:

The solution was obvious, but couldn't think of it immediately. So by writing it down here I'm sure I'll never forget.

Add the hostname to /etc/hosts!

I installed a renewed SSL certificate on a webserver (Apache 1.3), replacing the old certificate with the newer one. However, when one checks the SSL page in the internet browser, the data of the old certificate may be seen. This is a known issue with Apache. But restarting the webserver did not work out. But it turned out that I didn't start the server with SSL support. These are the commands which should be issued after replacing a certificate:

And after this command the new certificate was shown in the browser.