security issues

The other day I had a tech come and help troubable shoot my network.I asked if it was normal for my admin tool page to say it isnt secure and he said it was chroma to use enternet explore so I di and this is what happened there 

The hostname in the website’s security certificate differs from the website you are trying to visit.
Error Code: DLG_FLAGS_SEC_CERT_CN_INVALID is this should I worrie