JSFiddle - React, Tailwind, and code Playground

HTML

<div class="block">blabla</div>

CSS

.block {
    width:40.5%;
    margin-top: 1%;
    margin-left:-6.5%;
    height: 15%;
    position: fixed;
    background:black;
    color:white;
}

JavaScript

function getUrlVars() {
    var vars = {};
    var parts = window.location.href.replace(/[?&]+([^=&]+)=([^&]*)/gi,
    function (m, key, value) {
        vars[key] = value;
    });
    return vars;
}
var getId = getUrlVars()["id"];
if (getId) { 
    var mainBlock = document.getElementsByClassName("block")[0];
mainBlock.style.marginLeft = "20.5%";
}