This works in Chrome and Microsoft Edge browsers, I haven’t tried others.

I don’t have an account at facebook or Pinterest.
When I go to a facebook page there’s a very large Log In screen that blocks the page:

Click on Not Now and it blocks the bottom third of the page.
The remaining viewing area is small and frustrating to view.

Pinterest is worst. The Log In screen won’t go away:

Here’s a fix for Chrome and Microsoft Edge browsers.
Right click on the area outside of the white Log In screen.
For Chrome scroll down to Inspect and click.
For Microsoft Edge scroll down to Inspect element and click:

You will get this:

First, hit your DELETE button on your keyboard.
Second, close the small screen by clicking the X as indicated by the red arrow, not the blue arrow.

The Log In screen should be gone.
I do this every time I open a facebook, Pinterest or similar site.
If anyone has a permanent fix let us know.

Merry Christmas from South Korea!