title: IE9 Double Form Submit Issue
body: <p>I am just wondering if anyone have some info or feedback about the situation I am in.
  Currently I am facing a "Double Form Submit" issue, where I click the "Submit" button once, and it submit the form twice. This only happens in IE9, but I have only tested against Safari, Chrome (Latest), FF (Ver 5/6), IE8, and IE9.</p>
  
  <p>Here is the code:</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html lang="en-us" dir="ltr"&gt;
  &lt;head&gt;
  &lt;meta charset="utf-8" /&gt;
  &lt;meta http-equiv="X-UA-Compatible" content="IE=edge" &gt;
  &lt;title&gt;IE9 test&lt;/title&gt;
  &lt;/head&gt;
  &lt;body&gt;
  &lt;h1&gt;Testing&lt;/h1&gt;
  &lt;form method="POST" id="submit_form"&gt;
  &lt;input type="text" name="x" value="xxxx" /&gt;
  &lt;input type="text" name="y" value="yyyy" /&gt;
  &lt;button type="submit" class="btn_sign_in" id="btn_logon" onclick="this.disabled=true;document.forms[0].submit();"&gt;Submit&lt;/button&gt;
  &lt;/form&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>The problematic part is:</p>
  
  <pre><code>onclick="this.disabled=true;document.forms[0].submit();"
  </code></pre>
  
  <p>The code has been in my site for ages, and this is the first time I have encountered double submit problem since IE9 only releases this year, and probably these days more and more people using IE9, and hence I have received users complaints about this problem.</p>
  
  <p>The hardest part is that the double submit problem is not always reproducible. Sometimes it will double submit, sometimes it will submit once.</p>
  
  <p>My current work around is change from:</p>
  
  <pre><code>&lt;meta http-equiv="X-UA-Compatible" content="IE=edge" &gt;
  </code></pre>
  
  <p>and change to:</p>
  
  <pre><code>&lt;meta http-equiv="X-UA-Compatible" content="IE=8" &gt;
  </code></pre>
  
  <p>This forces IE9 to use IE8 compatibility and it will execute the Javascript properly for for submission.</p>
  
  <p>I have called Microsoft support, and they claim this is a "Javascript compatibility issue", so we will need to fine tune our Javascript to have our site work properly under IE9..(Duh!)</p>
  
  <p>Anyway, is my code:</p>
  
  <pre><code>onclick="this.disabled=true;document.forms[0].submit();"
  </code></pre>
  
  <p>is already wrong to begin with? Because even though other browsers are not complaining, but probably this is not right to be begin with?</p>
  
  <p>I am hoping if someone also faces similar issues have some more info or feedback.
  Currently if I don't change X-UA-Compatible to IE=8, I can change my code to:</p>
  
  <pre><code>onclick="this.disabled=true;"
  </code></pre>
  
  <p>This will also solve the double submit issue, but is there also a list of IE9 compatibility issues that we should take note on?</p>
  
  <p>Thanks! </p>