Check the boxes for political boundaries, rivers etc. if you want them to appear on your map. If you would like to download a PostScript-version of your map after creation check the corresponding box. Then it has to be transfered to your browser. Once you received the map you can zoom in or out or define a new map center just by clicking into the map. Therefore, the value of the northern map boundary must be greater than the value for the southern and the value for the eastern boundary must be greater than the value for the western.
ZIP seems to be a compression format many platforms can handle.
The EPSF version of your map can be placed and printed from many DTP or WP programs. You might as well use Ghostscript for viewing and printing or format conversion. Location Plotting Plotting location maps is a standard task in geoscientific work. The strength of GMT is to plot these location in the proper projection - a tedious if not impossible business if you do it by hand. If you check the corresponding boxes these sites will be indicated on your maps by a white circle.