<form class="mainform">
<input placeholder="Имя*">
<input placeholder="Email*">
<br class="clear"/>
<textarea placeholder="Ваше сообщение*"></textarea>
</form>*{box-sizing:border-box;}
.mainform input{width:49%; float:left; margin:1%; padding:5px 10px;}
.mainform textarea{width:100%; padding:5px 10px; margin:1%;}
}