JSFiddle - React, Tailwind, and code Playground

HTML

<input type="email" name="email" placeholder="[email protected]" required />
<input type="url" name="website" placeholder="http://johndoe.com" required/>
<input type="text" name="name" placeholder="John Doe" required/>

CSS

input:required:invalid, .contact_form textarea:required:invalid { /* when a field is considered invalid by the browser */
    background: #fff url(images/invalid.png) no-repeat 98% center;
    box-shadow: 0 0 5px #d45252;
    border-color: #b03535
}

input:required:valid, .contact_form textarea:required:valid { /* when a field is considered valid by the browser */
    background: #fff url(images/valid.png) no-repeat 98% center;
    box-shadow: 0 0 5px #5cd053;
    border-color: #28921f;
}