In a Single: Yes, it should be saved automatically, and infinitely AFAIK. You have the choice to contine once you get back to the main game menu.
In a Multiplayer: Yes, as long as you manage to return within the 5 mins waiting time given AND your group has the patience to wait for you. Should be plenty to close down and restart the browser and return to WGT, it may be close when you have to restart your computer.