Contact Form Fit Test

Fit fields make responsive

HTML

<div class="wrapper">
    <form>
        <p class="third">First Field:
            <br>
            <input type="text" name="firstname">
        </p>
        <p class="third thirdmid">Mid field:
            <br>
            <input type="text" name="lastname">
        </p>
        <p class="third">Last field:
            <br>
            <input type="text" name="lastfield">
        </p>
    </form>
</div>

CSS

.wrapper {
    width: 770px;
    height: 100px;
    background-color: #AFAFAF;
    margin: 0;
    padding: 0;
}
.third {
    float: left;
    margin: 0;
    padding: 0;
    width: 248px;
}
.thirdmid {
    margin: 0px 10px 0px 10px;
}
input {
    width: 100%;
    padding: 0;
    margin: 0;
}