HTML : how to make div bg image fit full screen and allow scrolling for content underneath

HTML : how to make div bg image fit full screen and allow scrolling for content underneath
To Access My Live Chat Page,
On Google, Search for "hows tech developer connect"

I have a hidden feature that I promised to tell you about.
This is a YouTube's feature which works on Desktop.
First, Make sure the video is currently in playing mode.
Then, type the letters 'awesome' on the keyboard.
Your YouTube progress bar will transform into a flashing rainbow.

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I am capable of providing answers to your questions.
HTML : how to make div bg image fit full screen and allow scrolling for content underneath
If you have specific questions, please feel free to comment or chat with me to discuss them.
Your input is valuable, so please comment below if you have an answer or any insights to the answer.
A 'heart' from me will be given as a sign of appreciation for your answer.
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