Dynamic CSS site tutorial: Multiple page styles provide viewers with choices_CSS/HTML

I saw this code for instant STYLE change on cnbruce's blog. I thought it was good and copied it for later use.
The example I saw is: there are multiple page styles on a website for viewers to choose. .At the same time, after selecting a certain style, when you open the page again, the style will still be maintained. Naturally, Cookie technology comes to mind.

Program code

Please select the drop-down menu below to test the skin resurfacing effect

css.css
css1.css
css2.css
< ;a href=# onclick="changecss(''css3.css'')">css3.css

Select stylesheet file