Hi,

Please check the code I created below:

<label for="website-select">Choose a website:</label>
<select id="website-select" onchange="redirectToWebsite()">
    <option value="">--Select an option--</option>
    <option value="https://www.google.com">Google</option>
    <option value="https://www.facebook.com">Facebook</option>
    <option value="https://www.twitter.com">Twitter</option>
</select>
<script>
function redirectToWebsite() {
    var select = document.getElementById('website-select');
    var url = select.value;
    if (url) {
        window.location.href = url;
    }
}
</script>

Regards,
PenciDesign.