<!-- AJUSTA A IMAGEM TAMANHO MAXIMO, FIXO, CORTANDO A MESMO CASO A JANELA SEJA REDIMENSIONADA-->
body {
  width: 100%;
  height: 100%;
  position: fixed;
  top: 0;
  left: 0;
  z-index: -100;
}

img {
  width: 20%;
  height: 10%;
}


<!--
body {
    background-attachment: fixed;
    background-image: url(plasma.JPG);
	background-repeat: no-repeat;
	background-position: center top;
    -webkit-background-size: cover;
       -moz-background-size: cover;
         -o-background-size: cover;
            background-size: cover;
}
    

img {
    width: 20%;
    height: 10%;
    background: transparent;    
}    

    
h1, h2, h3, h4, h5, h6 {
    color: #222;
    font-weight: 600;
    line-height: 1.3em;
    background: transparent;        
}

h2 {
    margin-top: 1.3em;
    background: transparent;        
}
-->