You can find the dimensions of any image on a webpage by putting your pointer on the image and RIGHT CLICKING, then select "Inspect" from the context menu.  That will open a window or a pane to the background coding of the page.  That pane should be on the image filename itself.  Now, hover your mouse pointer on that filename in the inspection pane.  It should popup and show you the dimensions in use for that image.  There are two sets of numbers.  The natural (actual) size of the image and the size that it is currently being displayed at in your current browser session.