body {
 font-family: Verdana, Arial, Sans-Serif;
 font-size: 1rem;
 background: Whitesmoke;
 margin: 25px;
}

input,
button {
 font-family: Verdana, Arial, Sans-Serif;
 font-size: 1rem;
 border: 1px solid #AAAAAA;
 padding: 5px;
}

input:required:invalid,
textarea:required:invalid {
 border-left: 2px solid #EE0000;
}

input:required:valid,
textarea:required:valid {
 border: 1px solid #AAAAAA;
}

input[name="name"],
input[type="mail"] {
 width: 300px;
}

input[name="betreff"] {
 width: 380px;
}

textarea {
 font-family: Verdana, Arial, Sans-Serif;
 font-size: 1rem;
 width: 400px;
 min-width: 400px;
 height: 260px;
 min-height: 260px;
 padding: 5px;
}

span.hilfetext {
 font-family: Arial, Tahoma, Sans-Serif;
 font-size: 0.80rem;
 font-style: Oblique;
 color: #00AE00;
}