[css] align divs to the bottom of their container

I figured this would be simple, I need to align both of the inside divs (green and blue) to the bottom of their container (red). I'm hoping to not use absolute positioning and i need it to be ie6,7,8 ff chrome safari etc compatible.

<div style="border:1px solid red;">
    <div style="border:1px solid green; width:20px; height:20px; float:left;"></div>
    <div style="border:1px solid blue; width:20px; height:30px; float:left;"></div>
    <div style="clear:both;"></div>
</div>

i've tried using vertical-align but can't find a simple solution.

thanks for the help, p.

EDIT here's my attempt at abs pos solution:

<div style="border:1px solid red; position:relative;">
    <div style="border:1px solid green; width:20px; height:20px; float:left; position:absolute; bottom:0px;"></div>
    <div style="border:1px solid blue; width:20px; height:30px; float:left; position:absolute; bottom:0px;"></div>
    <div style="clear:both;"></div>
</div>

I don't like absolute positioning, either, because there is almost always some collateral damage, i.e. unintended side effects. Especially when you are working with a responsive design. There seems to be an alternative - the sandbag technique. By inserting a "helper" element, either in the markup of via CSS, we can push elements down to the bottom of the container. See http://community.sitepoint.com/t/css-floating-divs-to-the-bottom-inside-a-div/20932 for examples.

You can cheat! Say your div is 20px high, place the div at the top of the next container and set

position: absolute;
top: -20px;

It may not be semantically clean but does scale with responsive designs

The way I solved this was using flexbox. By using flexbox to layout the contents of your container div, you can have flexbox automatically distribute free space to an item above the one you want to have "stick to the bottom".

For example, say this is your container div with some other block elements inside it, and that the blue box (third one down) is a paragraph and the purple box (last one) is the one you want to have "stick to the bottom".

By setting this layout up with flexbox, you can set flex-grow: 1; on just the paragraph (blue box) and, if it is the only thing with flex-grow: 1;, it will be allocated ALL of the remaining space, pushing the element(s) after it to the bottom of the container like this:

(apologies for the terrible, quick-and-dirty graphics)

The modern way to do this is with flexbox, adding align-items: flex-end; on the container.

With this content:

<div class="Container">
  <div>one</div>
  <div>two</div>
</div>

Use this style:

.Container {
  display: flex;
  align-items: flex-end;
}

https://codepen.io/rds/pen/gGMBbg