With the "small" Mac keyboard, how to simulate a HOME, END, and PageUp, PageDown key?
The Command+Up/Down keys you mentioned for Chrome and Safari are coincidences. The Fn+Up/Down keys are not. Those key combinations are actually mapped to the Page up/Page down keycodes, so the application thinks you actually pressed those keys. There are similar mappings for Home and End: Fn+Left and Fn+Right, respectively. These Fn+Arrow mappings will work exactly like Page Up/Down and Home/End in any application, unless it somehow is working around the system.