body
{
  margin: 0;
  font-size: 1.3em;
}

@media (max-width:600px)    /* small */
{
	#navContent
	{
	  width: 30%;
	}

	#mainContent, footer
	{
	  margin-left: 30%;
	}
	body
	{
		background-color: red;
		color: white;
	}
}

@media (min-width:601px)    /* medium */
{
	#navContent
	{
	  width: 30%;
	}

	#mainContent, footer
	{
	  margin-left: 30%;
	}
	body
	{
		background-color: blue;
		color: white;
	}
}

@media (min-width:993px)    /* large */
{
	#navContent
	{
	  width: 25%;
	}

	#mainContent, footer
	{
	  margin-left: 25%;
	}
	body
	{
		background-color: gray;
		color: black;
	}
}