Position third horizontal div to the bottom of other divs? - html

Question

EDIT: The problem is solved, so thanks to everyone who helped!
Original post:
So I am trying to put three divs next to each other (until thus far this part has been successful) with the third and last div to like go to attach to the bottom of the divs, which I have no clue how to do this.
How can I put the third div to attach to the bottom of the middle div and stay within the container?
To show you, I made a quick example. Something like this:
The black colour in the image is the 'body'.
The grey is a container div I put the three other divs in.
Each other box represents a div with what I want them to do and how approx. I want them to be positioned of one another.
I hope this can be done only using html and css. I would appreciate any help.
So far I have this as html for the divs:
#nav,
#textarea,
#contactallpages {
vertical-align: top;
display: inline-block;
*display: inline;
}
#containerpage {
position: relative;
margin: auto;
padding-top: 5%;
padding-bottom: 5%;
background-color: black;
height: 100%;
width: 70%;
}
#centercontainer {
background-color: lightblue;
width: 75%;
margin: 0 auto;
padding: 2%;
}
#nav {
float: left;
background: #aaaaaa;
height: 50%;
width: 15%;
padding: 1%;
}
#textarea {
display: inline-block;
background: #cccccc;
height: 70%;
width: 64%;
padding: 1%;
}
#contactallpages {
background: #bbbbbb;
position: absolute;
width: 15%;
padding: 1%;
bottom: 0;
}
<div id="containerpage">
<div id="centercontainer">
<div id="nav">
<ul>1
</ul>
<ul>2
</ul>
<ul>3
</ul>
</div>
<div id="textarea">
<header>
<h1>Welcome</h1>
</header>
<p>
Text text more text.
</p>
<p>
And more text.
</p>
</div>
<div id="contactallpages">
Random small textbox
<br>More small text.
</div>
</div>
</div>

Answer 1

The way you should lay this out is one container div and 3 children div's set to display: inline-block;
Using display: inline-block; will position all the div's next to each other and allows you to use the vertical-align property.
Now all you would need to do is set the proper vertical-alignment for each of the child div's. You can also set the height to the container div (#myPage) and that is the height that vertical-align will use to determine the positioning.
https://developer.mozilla.org/en-US/docs/Web/CSS/vertical-align
#myPage div {
display: inline-block;
width: 100px;
}
#centerFold {
height: 200px;
vertical-align: middle;
background-color: yellow;
}
#navBar, #contact{
height: 100px;
}
#navBar {
vertical-align: top;
background-color: red;
}
#contact {
vertical-align: bottom;
background-color: blue;
}
<div id="myPage">
<div id="navBar">
</div>
<div id="centerFold">
</div>
<div id="contact">
</div>
</div>

Answer 2

Try out flexbox if you do not have too much to worry about backward compatibility. My time at the moment doesn't allow to elaborate, but the essential part would be
#centercontainer {display: flex}
#contactallpages {align-self: flex-end}
Be aware though that some prefixing will be necessary for older browsers and this is only the standards-compliant solution. It does everything you want and you can forget about floating. Adding a
#textarea {flex-grow: 1}
would even allow the center to grow not only in height but in width also.