body{
  background: #eee url(../images/img01.jpg) repeat-x fixed top;
  background-color: #ecebee;
}

h1, h2, h3 h4, h5, h6, p {
  font-family:'Montserrat', Helvetica, Arial, sans-serif;
}
 
.header_img{
  width: 330px;
 }

 .img_medium{
   width: 150px;
   height: 90px;
 }

 
/*-----------------------------------------------------   
     Tabletversion ab 640 Pixel                          
       640px / 16px/em = 40em  
------------------------------------------------------*/
@media screen and (min-width: 40em) {
  .header_img{width: 450px; visibility: visible;}
  
  
  }
  
  /*------------------------------------------------------------------
      Bildschirme ab 1024 Pixel                         
        1024px / 16px/em = 64em	
   ------------------------------------------------------------------- */
   @media screen and (min-width: 64em) {
       .header_img{width: 650px;}
  
  }	    
  /*------------------------------------------------------------------- 
      Große Bildschirme (>1280 Pixel) 
        1280px / 16px/em = 80em
    -------------------------------------------------------------------- */
  @media screen and (min-width: 80em) {
      .header_img{width: 750px;}
  
  }