index.html

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <link rel="stylesheet" href="style.css">
  <title>Temperature Converter</title>
</head>
<body>
  <div class="container">
    <div class="converter">
      <h1>Temperature Converter</h1>

      <div class="input-group">
        <input type="text" id="temperatureInput" placeholder="Enter temperature" oninput="validateInput()">
        <select id="inputUnitSelector">
          <option value="celsius">Celsius</option>
          <option value="fahrenheit">Fahrenheit</option>
          <option value="kelvin">Kelvin</option>
        </select>
      </div>

      <button onclick="convertTemperature()">Convert</button>

      <div id="resultArea"></div>
    </div>
  </div>
  <script src="script.js"></script>
</body>
</html>