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<html><title>W3.JS</title><style>.class1 { background-color: orange; font-size: 30px; color: white;}.class2 { padding: 20px; border: 5px solid red;}</style><script src="https://www.w3schools.com/lib/w3.js"></script><body><h2>Testing W3.JS in HTML</h2><p>Click the button to add class='class1 class2' to id='London'.</p><button onclick="w3.addClass('#London','class1 class2')">Add Classes</button><div id="London" class="city"> <h2>London</h2> <p>London is the capital city of England.</p></div><div id="Paris" class="city"> <h2>Paris</h2> <p>Paris is the capital of France.</p> </div><div id="Tokyo" class="city"> <h2>Tokyo</h2> <p>Tokyo is the capital of Japan.</p></div></body></html>