quick question are you wrapping the html content into an already existing page?
eg
<html>
<head>
</head>
<body>
My Inserted File
</body>
</html>
or are you just rendering whatever is in the file?
Can you try adding something like this to your hta setup
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
It's rendered in an iframe.
I can't include the meta tag in the TD application because it will affect the entire app, and that's going to require a lot of change to make it work (trust me, I've already gone down that path). The app doesn't work
at all in standards mode. It will need a lot of work.
I seem to be getting my layout to render somewhat in html5, still not supporting border-radius for whatever reason. Oddly enough if I just save the html file with a .hta extension it displays properly.
The filename you choose should have no effect, since the file is loaded by the application and then saved to a temporary file (after doing token replacement) with the filename extension .html.
Also from what I've read IE-9 and above will render child frames / iframes in standards mode. It won't however deal with modals and other html 5 windowed elements very well rendering them in ie 8
Honestly I can't remember
exactly what won't work right, but the TD uses a lot of modal dialogs (the entire Settings window is a modal dialog), so that presents an issue. I could see moving to standards mode even if modals remained in compatibility mode just so the layout could utilize HTML 5 (and I may yet end up doing that), but that still presents some other issues that will have to be dealt with.