Q:

height 100% doesn't work, two divs inside div

See css: http://jsfiddle.net/4JgA4/114/
Also here:
<div style="min-height:40px; border:solid 1px black; float:left;">
      <div style="border:solid 1px black; height:150px; float:left;">
       First to set height
      </div>

       <div style="border:solid 1px red; height:100%; float:left;">
      Why don't get the 100%
    </div>
</div>

Why does the second div doesn't get the 100%?

A:

<div style="min-height:40px; height:150px; border:solid 1px black; float:left;">
    <div style="border:solid 1px black; height:100%; float:left;">
    Your text 1
    </div>

    <div style="border:solid 1px red; height:100%; float:left;">
    Your text 2
    </div>
</div>

The reason is you didn't put exact height (150px) for the first .
One more thing, you have already put exact height for th first height, you only need to height = 100% for inside tags.

Here is the result: http://jsfiddle.net/4JgA4/117/

