How can I add shadow to a button in HTML?
To add a shadow to a button in HTML, you need to use CSS styling. There are a couple ways to use CSS styling, however, I'm going to be using the internal method with the <style> tag. Here is how to add shadow to a button in HTML:

```xml
<html>
    <head>
        <style>
            button {
                box-shadow: 5px 5px 10px darkgrey;
        </style>
    </head>
    <body>
        <button type=button>Click me!</button>
    </body>
</html>
```

Let me know if you have any more questions!