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Bootstrap class: .is-invalid

    <form class="row g-3">
        <div class="col-md-4">
            <label for="validationServer01" class="form-label">First name</label>
            <input type="text" class="form-control is-invalid" id="validationServer01" value="123456" required>
            <div class="invalid-feedback">
                Please enter your name.
            </div>
        </div>
        <div class="col-md-4">
            <label for="validationServer02" class="form-label">Last name</label>
            <input type="text" class="form-control is-invalid" id="validationServer02" value="" required>
            <div class="invalid-feedback">
                Please enter your last name
            </div>
        </div>
    </form>

Preview

Please enter your name.
Please enter your last name

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