Summary
Acunetix 360 identified an invalid SSL certificate.
An SSL certificate can be created and signed by anyone. You should have a valid SSL certificate to make your visitors sure about the secure communication between your website and them. If you have an invalid certificate, your visitors will have trouble distinguishing between your certificate and those of attackers.
Impact
Attackers can perform man-in-the-middle attacks and observe the encryption traffic between your website and its visitors.
Remediation
Fix the problem with your SSL certificate to provide secure communication between your website and its visitors.