HTML
<!DOCTYPE html>
<html>
<head>
<title>Problema</title>
<link rel="StyleSheet" href="estilos1.css" type="text/css">
</head>
<body>
<div id="contenedorform">
<form method="post" action="#">
<label>Ingrese nombre:</label>
<input type="text" name="nombre" class="texto1">
<br>
<label>Ingrese email:</label>
<input class="texto2" type="text" name="mail">
<br>
<label>Comentarios:</label>
<textarea class="texta" name="comentarios"></textarea>
<br>
<input class="botonsubmit" type="submit" value="confirmar">
</form>
</div>
</body>
</html>
CSS
#contenedorform {
width:500px;
height:250px;
margin-left:20px;
margin-top:10px;
background:#A3F5FB;
border:1px solid #CCC;
padding:20px;
-webkit-box-sizing: border-box;
-moz-box-sizing: border-box;
box-sizing: border-box;
}
#contenedorform form label {
width:120px;
float:left;
font-family:Arial;
font-size:17px;
}
.texto1 {
width:300px;
background-color:#E4FBFC;
border: 1px solid grey;
margin-left:10px;
}
.texto2 {
width:300px;
background:#E4FBFC;
border: 1px solid grey;
margin-left:10px;
}
.texta {
width:297px;
height:130px;
background:#E4FBFC;
border: 1px solid grey;
margin-left:10px;
margin-top:10px;
}
.botonsubmit {
color:#f00;
background-color:#bbb;
border: 1px solid #fff;
}