body{ 
background: url(tlo.jpg) no-repeat;  
background-size: cover;  
-moz-background-size: cover;  
-o-background-size: cover;
display:block;  
width:99%;  
height:100%;  
position:absolute;  
overflow:auto;  
}

#cala_strona {width: 900px;
margin: 2px auto;}