What all the information on the page means
Race Data Sheet
This is the technical stuff,containing all the details of how the course was measured.This is what is sent to the Course Measurement Secretary for verification so that the Certificate of Accuracy can be issued. The only part of the sheet which will probably be of interest is the descriptions of the start and finish and mile or KM marks.This information will be duplicated on the photo sheets anyway. It is a Microsoft Excel file,which can also be read by other programmes such as Open Office
Google Earth File
This is a *.KML file which will open in Google Earth.You need to have Google Earth installed on your computer.Depending on your computer set up,you can either click the link to go straight to Google Earth,or you may need to save the linked file to your computer first(usually,right click and "save as") This method has the advantage of the mile marks being in the exact place that I recorded them,rather than where the mapping programme thinks they should be.
There will usually be an embedded map of the course displayed on the race page,either Good Run Guide, Map my Run, or Google Maps.In all cases ,there will be a link(usually underneath the map frame) to take you to a full screen version of the map. The maps in all cases are zoomable to help in locating mile marks etc,and can be switched between satellite view and road maps.
Measurements using mapping sites can sometimes be misleading. Have a look at Why Map my Run is Rubbish