For those of you that are diligently testing the bounds of the web using, you may have noticed some issues when debugging GWT apps within Internet Explorer 9. Google has provided a workaround to get you working in Development Mode again.
Note 1. this's only an issue when running your GWT app in Development Mode under IE 9. Production Mode is unaffected.
2. Until this issue is resolved, you'll need to do this for each HTML host page in order to use GWT dev mode with IE9.
The current workaround is to avoid document mode 9. To force an earlier document mode, add a meta tag to your html files indicating a different document mode. For instance, in the case of the sample GWT app html page, add
<meta http-equiv="X-UA-Compatible" content="IE=8" /> to the
<head> section as shown below: