Google released Chrome 42 last week, and as users have upgraded, they've seen a warning about the SSL certificates installed on a number of Stanford websites. A red X and line appear in the lock icon and "https" of the URL.
This warning is displayed for certificates that are signed with an older encryption algorithm. It is not an indication that there's a current security problem with the site or certificate—this is Chrome's way of encouraging more rapid adoption of stronger encryption.
While new certificates that Stanford issues are signed with stronger encryption methods, issues with some older operating systems and applications prevent University IT from deploying newer certificates across all sites right now.
In the meantime, this specific warning in Chrome 42 and later versions can be safely ignored. For more information about this warning and the reasons behind it, please see this post from Google's security blog.