title: How to make text input w/button autosize within responsive div
body: <p>I am working with a website that is already responsive and works fine. I am trying to add a text input field with a button on the right and want the text input to autosize and the button to remain a fixed size.</p>
  
  <p>The general HTML/CSS is:</p>
  
  <pre><code>&lt;style&gt;
    #container { width: 100%; }
    #text { float: left; }
    #btn { float: left; overflow: hidden; }
  &lt;/style&gt;
  
  &lt;div id="container"&gt;
    &lt;div id="text"&gt;&lt;input type="text" /&gt;&lt;/div&gt;
    &lt;div id="btn"&gt;&lt;input type="submit" /&gt;&lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>A visual:</p>
  
  <pre><code>+---------------- container (autosize) --------------+
  | +------------------------------------------------+ |
  | |        text (autosize)        |       btn      | |
  | +------------------------------------------------+ |
  +----------------------------------------------------+
  </code></pre>
  
  <p>Desired behavior:</p>
  
  <p>The container div will autosize depending on display width - this already gets handled. The btn div will size to exactly the width of the button - this already gets done also.</p>
  
  <p>I would like the text input div to autosize with the text input to be 100% of the text div.</p>
  
  <p>Is this possible? I think I've given enough info but am happy to provide any other details needed. I've been working on this for hours and am frustrated at this point.</p>
  
  <p><strong>EDIT</strong></p>
  
  <p>I may not have explained the desired behavior clearly enough. </p>
  
  <p><code>#container</code> width changes according to display width. This already happens perfectly. It can be 960px width all the way down to 320px width.</p>
  
  <p><code>#btn</code> is not a fixed width. It will be positioned all the way to the right margin of <code>#container</code>.</p>
  
  <p><code>#text</code> width needs to autosize to take up the entire width between <code>#container</code>'s left and <code>#btn</code>'s right margins.</p>