Agree with YJ on playing with ONLY the WGT play window open, though I cheat a bit: I play using Comodo Dragon, while I have another browser (Chrome) open to multi-task, usually on http://www.wgtls.co.uk where I meet with other on-line golfers to set up matches, etc. I also use GameBooster to stifle other background activity like updates, that can inject noise into the game.
To set up Comodo to open up on the WGT play window, click on the Dragon logo in the upper left corner of the window, and choose 'Settings...' , go to 'On Startup' and click the button for 'Open a specific page or set of pages. Set pages
Click the Set pages button and enter the following url: http://www.wgt.com/gameclient.aspx
Now when you open Comodo Dragon, you'll automatically go to the WGT play window.
WARNING! Do NOT open up WGT main page in another browser type (Chrome, Firefox, etc.)! Subtle differences in coding between the various browser types can lead to game errors. If you absolutely have to have WGT main window open, then open it in a new tab in Comodo Dragon. Still, close it out when actually shooting a shot for best meter results.