If you’re like me, you make use of a lot of widget links within Magento, and those Widget links have a pesky habit of adding ?___store=default to the end of your URLs, which first of all don’t look nice and it certainly doesn’t help your optimisation efforts when it comes to SEO and ridding yourself of duplicate content.
This is a dead simple fix, and gives you peace of mind.
Simply copy the follow file: app/code/core/Mage/Catalog/Block/Widget/Link.php and paste it into app/code/local/Magento/Catalog/Block/Widget/Link.php
Then lines 89 – 92 need to be commented out. These lines look like this: (if it changes in future versions!)