John Mueller of Google reshared a post on Google+ originally shared by Google's Ilya Grigorik with information on a tool that helps webmasters find and ultimately fix those hard to find mixed content issues on your site. You know, when you have a web page someone on your site that has something embedded using HTTP, on your HTTPS page, which results in a broken HTTPS/SSL lock at the top of your browser.
This tool will help you find it. The tool is at report-uri.io and it will scan your pages for the issue. This blog post by Scott Helme, an Information Security Consultant, goes through how it works.
You can find the full array of tools over here.
Keep in mind, currently, having mixed content HTTPS errors doesn't impact your Google HTTPS ranking boost but it may one day.
Forum discussion at Google+.
