What is the function of the question mark after the name of the externally imported CSS file_html/css_WEB-ITnose

What is the function of the question mark after the name of the externally imported CSS file:

When you look at the code of the web page, you sometimes find that the

Maybe you think that the characters after the question mark are It has a special meaning, but it is not the case. It can be modified to any character. It is like a version number of this CSS file. For example, after the web page is visited, the original CSS style may be stored in the cache, although the server may The CSS file has been updated, but the browser cannot get the update. If you add a question mark and the following characters, the CSS style of the web page can be updated in time.

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