If your HTML files are within the same directory as the WebToons, you only have to use relative URLs, not absolute path URLs. In order to link to a section within your HTML document, you will need to edit your HTML document and add anchor tags, with NAME attributes, at the top of the section. Your image must be in its final dimensions. I use the UNIX utility xv or Photoshop to measure image coordinates. It is important that your clickable regions do not overlap or share coordinates.
Image coordinates are two-dimensional, measured in pixels.
The diagram below may clarify. I have sketched in temporary rectangles to roughly approximate the balloons. The x,y coordinates are separated by commas, and pairs of coordinates are separated by commas. If one rectangle is 0,0,200,75 then the one below it would start at 0,76 not 0,75. I determine the coordinates by looking at the image in Photoshop, and setting the cross-hair section of the Show Info palette to pixels.