Why doesn't the preload window appear when using OpenServer?

Question

css

Good evening!
There was an incomprehensible situation.
I am doing a preload for a site and when I separate the CSS code into a .css file, and into JS into a .js file, then the preload does not work from the word at all,
but if I use CSS and JS code in the html file, then everything works.
And again, if I separate the CSS code into a .css file, and into JS into a .js file and enter the site through the .html file, then the preload works.
What could be the reason for this situation?

Answer 1

when i split css code into .css file and JS into .js file, preload doesn't work from word at all

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