On many sites when connecting the table at the end of the address, after ? incomprehensible numbers are passed

<link href="http://www.htmlbook.ru/ie/rus/x3.css?1234">

What are these numbers for 1234? What can they do? If the question is a button accordion, I apologize, the search did not give results

    1 answer 1

    There are several options:

    1. The most banal - we transfer some parameter to "reset the cache" for this file. The parameter has changed / appeared - it means you need to re-request the file. Judging by the visibility of the parameter: 1234 - this is the case.
    2. css is generated dynamically depending on the parameter.
    • 2 point please explain - oxyage
    • one
      roughly speaking: if ($ _REQUEST ['param1'] == 12345) {echo 'background-color: black;';; } else {echo 'background-color: white;';; } - Alex Kapustin