1. .contenedor { overflow: auto; }
  2.  
  3. .div1 { float:left; width:440px;}
  4. .div2 { float:right; width:440px;}
  5.  
  6. #header {
  7. height: 100px;
  8. background: #0072b8;
  9. font-family: Arial;
  10. font-size: 16px;
  11. color: white;
  12.  
  13. }
  14.  
  15. <div id="header">
  16. <a href="home.html"><img src="http://placekitten.com/237/100" width="237px" height="100px" border="0" style="padding: 0 3.5em; float: left;"></a>
  17. </div>
  18.  
  19. <div class="contenedor">
  20. <div class="div1">
  21. <a href="http://placekitten.com/300/305" class="lightbox"><img src="http://placekitten.com/300/305" width="300px" height="305px"/></a>
  22. </div>
  23. <div class="div2">
  24. <a href="http://placekitten.com/300/305" class="lightbox"><img src="http://placekitten.com/300/305" width="300px" height="305px"/></a>
  25. </div>
  26. </div>
  27.  
  28. html {
  29. overflow-y:scroll;
  30. }