I am making a website over cyclists killed in Norway. For my project I have been using google maps api v3, but I have vague familiarity with javascript. You can see my resul
You need to attach the infowindow to the correct markers. Currently they are all associated with "marker", which doesn't exist (and should cause an error message in the javascript console when you click on the markers).
Inside the click listener change:
infowindow1.open(map, marker);
infowindow2.open(map, marker);
infowindow3.open(map, marker);
To:
infowindow1.open(map, marker1);
infowindow2.open(map, marker2);
infowindow3.open(map, marker3);
working example