Remove Store Query String
I recently developed a module to remove the store query string appended to the URL when you switch store views on the Magento frontend.
HOW IT WORKS
The module works by creating an Observer class to watch for the
controller_action_predispatch Magento event. This Observer class then removes both the
___from_store query strings from the URL before setting it in the controllerAction’s response.
You can view and download the code here on GitHub.
Once you have the module installed you can enable the removal of the store query string by going to the Magento Admin panel and navigating to System > Configuration > Web > Url Options.