With HTML5 capable browsers (including but not limited to Chrome 7+, Firefox 4+, IE 10+, Safari 6+), on the Attach page, the "Choose file" button
is replaced with a rectangle area on which you can drag and drop files.
With non-HTML5 capable browsers, the Attach page behaves as before.
As you see above, when an image file is dropped, its thumbnail is displayed.
You can remove a file from the uploaded file list by clicking the "Remove file" button.
If you click the "Drop files or click" area, a file dialog box shows up and you can choose multiple files from the box.
In contrast, the file dialog box shown by the "Choose file" button allows only one file to be selected at a time.