@jellytriangle IE10 is supported as well, but Chrome's internal spellchecker/use of spellcheck attribute is buggy.
Permitted File Extensions
Setting Permitted File Extensions for Add-ons
Each Add-on that is able to upload and display files - Image Manager, File Manager, Media Manager etc. - includes a Permitted File Extensions parameter to set the types of files that the add-on can upload and display.
The Permitted File Extensions Editor
To edit the Permitted File Extensions, click on the pencil icon adjacent to the Permitted File Extensions field in the parameters of the relevant add-on (eg: File Browser). The text field itself is not editable.
The Permitted File Extension editor will open displaying the list of extensions (file types) associated with the add-on, grouped by type, eg: Text, Images, Adobe® Flash®, Audio, Video, etc.
Extensions are represented by a rectangular box containing the extension icon, name and checkbox indicating the extensions status - checked = permitted, unchecked = not permitted. A permitted extension can be uploaded and will be displayed in the add-ons Browser list.
An extension box can be dragged within its group to re-order or between groups to move it to another group.
Extensions can be removed by unchecking the checkbox*
A new extension can be removed by clicking the remove button.
Extension Groups are represented by a rectangular box with the group name at the top, a drag handle on the left and a checkbox on the right indicating the group status.
Extension Groups associate extensions with a certain application or media type, eg: Microsoft Office® or Audio. Some add-ons such as the Media Manager use these groupings to determine how a particular media file is to be embedded. In some browsers such as IE, the groups are used as filters when selecting files to upload.
Each group contains an Add new type option, clicking on this will allow you to add a new extension to the group.
Groups can be re-ordered by drag and drop using the drag handle.
Removing Extension Groups
Extension Groups can be removed by unchecking the checkbox. Removing an Extension Group will remove all the extensions in that group*
Creating Extension Groups