Блочная верстка. Как сверстать три маленьких блока?

Ну давайте без div https://jsfiddle.net/5k8j0rht/

Может быть вам подойдет такой вариант: https://jsfiddle.net/5k8j0rht/27/ ?
Там конечно много чего допилить можно, но общая структура понятна.

Тож не понимаю что не так с дивами )

html:
div class="main"
div class="main_left" /div
div class="main_center" /div
div class="main_right" /div
/div

css:
.main {position: absolute; width: 100%; height: 20%}
.main_left {position: absolute; width: 33%; height: 100%; left: 0}
.main_center {position: absolute; width: 33%; height: 100%; left: 33%}
.main_right {position: absolute; width: 33%; height: 100%; right: 0}

Есть много вариантов абсолютное позиционирование одно из них

<footer id="boot">
		<ul class="flex cards">
			<li><h2>Card 1</h2>
			<p>Posuere varius ullamcorper ipsum adipiscing dignissim ipsum adipiscing a a quisque malesuada quam purus venenatis sagittis fermentum parturient curabitur montes a metus.
			</p>
			</li>
			<li><h2>Card 2</h2>
			<p>Posuere varius ullamcorper ipsum adipiscing dignissim ipsum adipiscing a a quisque malesuada quam purus venenatis sagittis fermentum parturient curabitur montes a metus.
			</p>
			</li> 
			<li><h2>Card 3</h2>
			<p>Posuere varius ullamcorper ipsum adipiscing dignissim ipsum adipiscing a a quisque malesuada quam purus venenatis sagittis fermentum parturient curabitur montes a metus.
			</p>
			</li>
		</ul>
	  
		<ul class="flex cards">
			<li><h2>Card 1</h2>
			<p>Posuere varius ullamcorper ipsum adipiscing dignissim ipsum adipiscing a a quisque malesuada quam purus venenatis sagittis fermentum parturient curabitur montes a metus.
			</p>
			</li>
			<li><h2>Card 2</h2>
			<p>Posuere varius ullamcorper ipsum adipiscing dignissim ipsum adipiscing a a quisque malesuada quam purus venenatis sagittis fermentum parturient curabitur montes a metus.
			</p>
			</li> 

		</ul>
 </footer>

/*flex*/

#boot {
	width: 100%;
	bottom: 0%;
	float: left;
	position: relative;
	z-index: 9;
	margin-bottom: 8em;
}

#boot {
	display: flex;
	flex-direction: row;
	flex-wrap: wrap;
	justify-content: center;
	align-items: flex-end;
	align-content: flex-end;
	padding-bottom: 1%;
}
.flex {
	display: flex;
	flex-direction: row;
	flex-wrap: wrap;
	justify-content: center;
	align-items: flex-end;
	align-content: flex-end;
}
.cards {
	list-style: none;
	margin: 0;
	padding: 0;
}
.cards li {
	border-radius: 5px;
	background-color: #00237E;
	color: #fff;
	flex: 1 1 200px;
}
.cards h2 {
	background-color: #00237E;
	margin: 0;
	font-size: 2vw;
	font-family: "BebasNeue Regular";
	color: #CFD8DC;
	padding-top: 1vw;
	padding-right: 1vw;
	padding-left: 1vw;
}
.cards p {
	padding-top: 1vw;
	padding-right: 1vw;
	padding-left: 1vw;
	padding-bottom: 1vw;
	float: right;
	font-size: 1.2em;
	font-family: Consolas, "Andale Mono", "Lucida Console", "Lucida Sans Typewriter", Monaco, "Courier New", monospace;
	line-height: 1.5em;
}
.flex li {
	margin: 0.5em;
}


@media (max-width: 1280px)  {
#boot {
	display: flex;
	flex-direction: row;
	flex-wrap: wrap;
	justify-content: center;
	align-items: flex-end;
	align-content: flex-end;
	padding-bottom: 1vw;
	padding-top: 1vw;
	padding-right: 1vw;
	padding-left: 1vw;
}
.flex {
	display: flex;
	flex-direction: row;
	flex-wrap: wrap;
	justify-content: center;
	align-items: flex-end;
	align-content: flex-end;
}
.cards {
	list-style: none;
	margin: 0;
	padding: 0;
}
.cards li {
	border-radius: 5px;
	background-color: #00237E;
	color: #fff;
	flex: 1 1 200px;
}
.cards h2 {
	background-color: #00237E;
	margin: 0;
	font: 2rem "BebasNeue Regular";
	color: #CFD8DC;
	padding-top: 2.5%;
	padding-bottom: 2.5%;
}
.cards p {
	padding: 5%;
	float: right;
	font-size: 1.4vw;
}
.flex li {
	margin: 0.5em;
}
	
}


@media (max-width: 800px)  {
#boot {
	display: flex;
	flex-direction: row;
	flex-wrap: wrap;
	justify-content: center;
	align-items: flex-end;
	align-content: flex-end;
	padding-bottom: 0%;
	padding-top: 0%;
	padding-right: 0%;
	padding-left: 0%;
}
.flex {
	display: flex;
	flex-direction: row;
	flex-wrap: wrap;
	justify-content: center;
	align-items: flex-end;
	align-content: flex-end;
}
.cards {
	list-style: none;
	margin: 0;
	padding: 0;
}
.cards li {
	border-radius: 5px;
	background-color: #00237E;
	color: #fff;
	flex: 1 1 200px;
}
.cards h2 {
	background-color: #00237E;
	margin: 0;
	font: 2rem "BebasNeue Regular";
	color: #CFD8DC;
	padding-top: 2.5%;
	padding-bottom: 2.5%;
}
.cards p {
	padding: 5%;
	float: right;
	font-size: medium;
}
.flex li {
	margin: 0.5em;
}

}