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I have the componente1 and the componente2 follow the example:
body {
  margin: 0;
}
.componente1 {
  width:250px;
  float: left;
  background-color: green;
  height: 340px;
}
.componente2 {
  width:250px;
  height: 340px;
  float:left ;
  background-color: red;
}
@media only screen and (max-width: 601px) {
  .componente1 {
margin-top: 345px;
  }
  .componente2 {
margin-top:-345px;
  }
}<div>
  <div class="componente1">
    
  </div>
  <div class="componente2">
    
  </div>
</div>Goal and do the componente2 stay above the componente1 in resolution below 600px width. This example works in IE and Chrome, but in Firefox 30px overwriting the componente1. 
Recalling that the answer has to be compatible with the main navigation vehicles.
Have you tried using percentage instead of pixel?
– KhaosDoctor
Already but I get very incompatible but try there sometimes you can do right.
– valdir silva
Can you put an example of how you want it to look? for me it looks like Chrome and FF... http://jsfiddle.net/cwdrhpke/show/
– Sergio
Replace "@media only screen and (max-width: 601px)" with "@media only screen and (min-width: 601px)", I use this a lot and have no problem and always use "min"
– ivan veloso