io credo tu faccia confusione tra padding e margin:

codice:
div#testata{
	margin-top: 90px;
	width: 700px;
	height: 150px;
	background-color: Blue;
	position:absolute;
	z-index:1;
}

div#colonnasx{
	margin-left: 70px;
	width: 150px;
	height: 800px;
	background-color: Olive;
	position:absolute;
}
ciaux