I went to sign into a website today using Google Chrome and was presented with the following error:


Your connection to this site is not fully secure
Attackers might be able to see the images you're looking at on this site and trick you by
modifying them

When I clicked the Details link It says the following

The site includes HTTP resources

I have never seen this warning before.
What does this warning mean in laymans terms and should I sign into the website with my username and password?
Extra:
Opening the same page in Microsoft Edge it claims the website is secure

In a nutshell, it is saying that while the core of the page is using https (secure) to get that information to your computer, that (secure) page references insecure elements (like pictures and possibly scripts).

Attackers can't directly change the original page, but they can change the insecure elements.  If those are pictures, they can change the image.  If those are scripts, they can change those, too.  In that way, attackers could change what you see, even though the core page was 'secure'.

As Michael Kjörling points out in the comments, this also exposes some of your information in these requests - potentially cookies (if it is the same site / matches the cookie sites / the developer didn't specify secure only), referrers, etc, which will leak some information about what you are doing at the best case and at the worse may allow certain attacks. 

This is bad practice on the part of the web developer - all elements should use secure transport.

You could (potentially) improve your own situation using a browser plugin that auto-updates all requests to http to https.  
