To add a blur effect to the shadow, use the box-shadow property.
You can try to run the following code to add blur effect
Example
<!DOCTYPE html>
<html>
<head>
<style>
h2 {
box-shadow: 10px 10px 7px green;
height: 50px;
background-color: yellow;
}
</style>
</head>
<body>
<h2>Heading Two</h2>
<p>Above heading has shadow.<p>
</body>
</html>