"Security Error: Domain Name Mismatch" occurs if you make a secure connection to a server whose domain does not match the domain name in the certificate it uses. This is to inform you that the site you are trying to connect to may not be the site you wanted. It may also occur when a site changes their domain name but doesn't buy a certificate for the new domain.
"Security Error: Server Certificate Expired" occurs if the site's certificate expiry date is later than your system date. This may be caused by your system having the incorrect time, or by the certificate genuinely being expired.
In both cases, you should make a judgment as to whether you still want to trust the server for what you want to use it for.
I believe this error message prodused from a bad advertisment and it is by design, it is not malware / adaware.
If you want to stop receive this pop-up and block advertisements from rmd.atdmt.com, just do this:
open your hosts file with notepad. Add the line as you see it in the end of the file:
127.0.0.1 rmd.atdmt.com
Hosts file usually located at:
c:\windows\system32\drivers\etc\hosts
What you saw,was a problematic advertisment, which inserted there from yahoo.
You can also inform yahoo about this, but follow above steps to put rmd.atdmt.com to hosts file and block them you'll be fine.
Best of Luck