You are recommended to add hku.hk to “Compatibility View Settings” to solve this issue
1. Click “Tools” on the top right hand corner of IE browser.
2. Click “Compatibility View settings“.
3. Enter “hku.hk” under “Add this website” box, and click “Add“. After clicking “Add“, click “Close” button to close the window.
4. You can then access the HTML editor when using IE.