The most minimalistic indicator of activity

... without javascript, without animated GIF, but not without frills. CSS is added to taste.

When is it needed?

• If you like to save on traffic and connections.
• If you do not like that animated image is loaded only at the end of the process.
• If you need to make a quick fix, but with taste.
• But who knows why else a good housewife may need such a useful thing as a minimalist indicator of activity .