certificate /etc/ssl/certs/cacert-class3.crt expiration warning

In the last 4 days root has been mailed to say that

Quote:

WARNING: certificate /etc/ssl/certs/cacert-class3.crt is about to expire in time equal to or less than 7 days from now on, or has already expired - it might be a good idea to obtain/create new one. NOTE: This message is being sent only once. A lock-file /var/run/certwatch-mailwarning-sent-cacert-class3.crt has been created, which will prevent this script from mailing you again upon its subsequent executions by crond. You dont need to care about it; the file will be auto-deleted as soon as you'll prolong your certificate.

What should I do?