Consider that you have a profile page, tabbed, and in one of the tabs you have a Google Map with the pinpoint of the user. When the page loads, it will load the map aplication, but the map div will not be visible at that point.
When you hit the map tab, you will see the map loaded, but, with some areas missing or acting really weird.
What is happening is when the tab loads, the map is not fully loaded and the main document finishs to load before the map loads, so, it understands that the map area is smaller than really is and shows it like that, funny.
How to fix it? Simplier than you think. If you search around you are going to find some stuff like map force redraw, but there’s a simplier way to do it.
Add a setTimeout to load the map.
That’s all you need and your map will have more than enought time to load all info and display correctly.