Popup.html

<!Doctype html>




<html>
<style>
.btn-group button {
    background-color: #4CAF50; /* Green background */
    border: 1px solid green; /* Green border */
    color: white; /* White text */
    padding: 8px 50px; /* Some padding */
    cursor: pointer; /* Pointer/hand icon */
    width: 100%; /* Set a width if needed */
    display: block; /* Make the buttons appear below each other */
}

.btn-group button:not(:last-child) {
    border-bottom: none; /* Prevent double borders */
}

/* Add a background color on hover */
.btn-group button:hover {
    background-color: #3e8e41;
}
</style>
<body>

<div class="btn-group">
  <button type="button" id="group" onclick="doGroup()">By Content</button>
  <button id="title" onclick="doTitle()">By Title</button>
  <button id="url" onclick="doUrl()">By URL</button>
  <button id="doAll" onclick="doAll()">Show All</button>
</div>
<script src="./background.js"></script>
</body>
</html>