Google Chrome is probably one of the stricter browsers out there in terms of highlighting SSL errors.
Most browsers will point out when you are viewing an HTTPS page which loads insecure images/Javascript, I understand how this is a security issue - an attacker could have modified the non-SSL content in a way which gives them access to the secure content, injected some javascript for example.
However once you have viewed an HTTPS page with mixed content, Google Chrome will continue showing you the mixed content warning (a red line through the 'https://') for as long as you stay browsing the same domain, even for subsequent pages which only include other HTTPS resources. Only once you navigate to another domain, or open a fresh tab does it tell you you're secure again.
What is the danger it's protecting you from here? How could mixed content on a previous page actually affect the security of subsequent secured pages? I understand that mixed content should be flagged up, but there must be a specific reason that Google is persisting this warning, other than "Well you still need to know about it"