What Larry is pointing out is that there is no information accompanying the image file that tells your browser how large the image should be on your screen. If you provide an image with more than the maximum resolution of the screen that displays it, the browser will enlarge the image until the display resolution is reached. For example, if you scan at 150 dpi (dots per inch) and the screen of the pc that is to display the pic can only display 75 dpi, you will see an image that is twice as large in each dimension (four times as large in area). Thus you will see more detail on the pc screen if the image is scanned at a higher resolution... but the detail will be in a picture that is larger than the original.

I've found that 150 dpi scan resolution works well, and gives an oversize image on the screen that shows all the detail you would find if you eyeballed the actual chip.