Can't download any image

Some website have script set to not allow downloads.

You would get a .webarchive if you attempted to save the web page itself instead of downloading a file.

Control click (right click) opens a contextual menu for copying, saving etc

You can always take a screen shot of your image if the resolution is suitable to you needs.

Some copyright permissions might well apply on some images scraped off the web.

If you want more help, you can post a link or webpage to the image in question, and I can look at the situation specifically.

Ok_lets see if we can sort this out—

To trouble shoot further you can:

Try a SafeBoot https://support.apple.com/en-us/HT201262

Takes noticeable longer to get to the login screen as certain system caches, dynamic loader cache etc get cleared and

rebuilt. This test will tell you if third party interference; extensions etc are not loaded in safe boot mode.

Test issue in another user (or guest user) account https://support.apple.com/en-us/HT204443

This will tell you if it a universal issue or isolated to your user/admin account.

You can also get a pretty good look at your system conf with the http://etrecheck.com, if there is third party interference

like user installed anti-virus etc.

Screen shots