I started getting this using chrome when viewing my companies intranet (internal internet) when I contacted my IT dept they explained that it was down to google and other browser manufacturers deciding that if your website was not up to date with the very latest of security certificates- obtainable from of course google and microsoft for a price, they would flag you up as a security risk, of course the companies internal internet was no more a risk than the company file servers, so its just the big companies way of forcing money out of the little guys, or else their websites are flagged as a security risk.