If you want to add a static .dfs2 grid on the map view, then you should add a Grid Overlay. If you add a time varying .dfs2 file the program will not object, but only the first time value will be displayed. If you add a .dfs2 file containing multiple items, such as a results file, you can select the grid item to display from within the file browser.
Transparency - This is used to control the way pixel colours are averaged for displaying images that overlay one another.
