# Custom mouseover on a layer
The mouseover is a popup window that is displayed after clicking on features on the map.
If no mouseover content is set in the layer configuration, no popup is displayed when clicking on a feature of that layer.
You can set your own mouseover content programatically in Javascript. For instance, you can add a mouseover on a layer that has no mousoever content in its configuration.
In the following example, the layer "Hydrography", id=3, has no mouseover defined.
We will set a custom mouseover content that:
* Always displays a custom header
* Displays the mouseover content for a clicked hydrography feature
* Avoids displaying a mouseover for the "Event" layer (blue dots on the map)
* Always displays a custom footer
## Set the custom mouseover
Try it out in [Codepen.io](https://codepen.io/k2-dev/pen/popjRrr?editors=1000)
```html
```
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