What is the main issue with the CSS design of the div in the code provided?

The main issue with the CSS design of the div in the code provided is that the width is set to a fixed pixel value (200px) which may not be responsive across different devices or screen sizes. To solve this issue, it is recommended to use percentage values for width to make the div responsive.

<div style="width: 50%;">
    <!-- Content goes here -->
</div>