unauthenticated content

[#1]

My Gmail has suddenly  started to show a padlock with a red line through it along with the message  "contains unauthenticated content"
Is this something I need to worry about and if not is there some way of turning it off.
Seems odd that it's just started as nothing has changed or been updated on my Gmail account.

[#2]

There`s some stuff about this on google..... something to do with viewing on https pages....
also there is this
https://support.mozilla.com/en-US/forum/1/15566
forum with some "possible causes"..... especially further down the page....

[#3]

Shutter,
Thanks for that.......One of the last posts under the name Duncan appears on that site which was from me. They notify you by e-mail if there are any responses to the post.
There are a number of suggestions about turning things off but I am a bit wary about that as other posts indicate it's not a good idea.

[#4]

Some of the "message boxes" that Microsoft put up really bug me..... like " Your printer is not working"...... [OK]      or "there is a fault with this program"    [ OK ].....  Actually, NO... it`s not OK.... but...
the only thing you can do is click on the OK button !....