Here is a description of the parameters that need to be passed. This will not work if custommap is not equal to true and the lats, lons, and zoom levels must be numeric and reasonable. Also, the layers must be valid in a comma delimited list, as mentioned below. There should be no whitespace in the URL. This could cause problems.
Also, there is protection against entering an invalid layer. If something comes close, the layer simply will not work. Finally, if a lat, lon, or zoom level is not numeric or is not in the valid range, 511 NY will perform existing tasks, such as checking for cookies, or displaying the default map.