2 floating div's side by side, with no width - html

Question

html
<div id="container">
<div id="one">One</div>
<div id="two">Two</div>
</div>
css
#container {
width: 500px;
height: 500px;
background-color: red;
}
#one {
width: 340px;
height: 100px;
margin: 20px;
background-color: green;
float: left;
}
#two {
width: 100px;
height: 100px;
margin: 20px 20px 20px 0px;
background-color: blue;
float: right;
}
This is what i want to do: http://jsfiddle.net/p4ZAd/
I want to make a margin of 20px between the two divs and this is how far Iv'e gotten, but is it possible to do it any other way?
What i would idealy like is to remove the width on the "#one" completely and just have it be maximum size with a margin towards the "#two".

Answer 1

LIke this
working fiddle
css
*{
margin:0;
padding:0;
}
#container {
width: 500px;
height: 500px;
background-color: red;
display:table;
}
#one {
background-color: green;
display:table-cell;
}
#two {
background-color: blue;
display:table-cell;
}

Answer 2

You can use table and table-cell display types to mimic how a table works. Then use border-spacing to accomplish the margin in-between cells.
HTML:
<div id="container">
<div id="one">One</div>
<div id="two">Two</div>
</div>
CSS:
#container {
display: table;
width: 500px;
height: 400px;
background-color: red;
border-spacing: 20px;
}
#one {
display: table-cell;
background-color: green;
}
#two {
display: table-cell;
width: 100px;
background-color: blue;
}
JSFiddle here
Here's a list of browsers that support display: table;

Answer 3

You can set padding on #container and then set negative right margin for #two. Example:
#container {
width: 360px;
height: 500px;
background-color: red;
padding: 20px 140px 20px 20px;
}
#one {
height: 100px;
background-color: green;
float: left;
width: 100%;
}
#two {
width: 100px;
height: 100px;
margin: 0 -120px 0 0;
background-color: blue;
float: right;
}
Working sample: http://jsfiddle.net/SytvY/1/