index.css

body {background-color:lightyellow; }

a {color:green; text-decoration:none;}
footer {clear:left; text-align:center; background-color:darkorange; }

header {
	background: url('imagenes/gimnasio.jpeg') no-repeat;
	background-size: 100% 100%;
	color: black;
	border-style:solid;
	margin-bottom:5%;
	display: flex;
	justify-content: space-between;
}
header img {margin-left:3%; margin-top:2%; width:150px; height:150px;}
header h1 { text-align:center; background-color:white; border-style:solid;
						width:30%; height:5%; margin-top:8%; margin-left:8%;}
header form {background-color:white; width:20%; height:20%; padding:2%; margin-top:4%; }
header section {background-color:white; width:20%; height:20%; padding:2%; margin-top:9%; }
.button {margin-top:2%;}

#izq img {width:90%; height:40%; margin-bottom:5%; margin-left:4%; }
#izq {float:left; width:50%; margin-left:5%; margin-bottom:5%;}

#der {list-style:none; text-align:center; font-size:250%; margin-top:7%; }
#der li {margin:4% 0%;}

#problema {text-align: center;}