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<html><body><p>A function is triggered when one of the input fields get focus. The function changes the background-color of the input field.</p>First name: <input type="text" id="fname" onfocus="myFunction(this.id)"><br>Last name: <input type="text" id="lname" onfocus="myFunction(this.id)"><script>function myFunction(x) { document.getElementById(x).style.background = "yellow";}</script></body></html>