The HTML <map> elements can be used to create image maps. Image maps are basically images with clickable areas on them, that can be hyperlinked to another web page or other parts of the same document. You can define which areas of an image are clickable by simply mentioning the corresponding X Y coordinates of those points in the <area> elements nested inside <map>.

Note: The clickable areas cannot be styled through CSS so, if you want those markers to be styled, use a simple image editing software to draw the markers.

Tip: If you want to know the coordinates for a point in an image, open the image in an image editing software and move the cursor to that point, you should be able to see the coordinates of it in the software itself. For GIMP it is shown at left side of the bottom bar.