This is an alternative way of opening a file. This is used when you have a file already on your hard disk and you already have an explorer window open in it's directory.
Simply drag the file onto Advanced HTML Optimizer. If Advanced HTML Optimizer is not visible (hidden behind another window) or minimized, drag the file down to the task bar and hover over Advanced HTML Optimizer (without releasing the mouse button). Advanced HTML Optimizer will then open to allow you to drop the file onto it.
To drag and drop: Point to an item, press and hold down the mouse button, and drag the image file to Advanced HTML Optimizer. Then release the mouse button.