You must have Google Analytics account level access to add filters.
- Log in to Google Analytics
- Click on your site's profile name.
- Click on "Admin" on the top navigation.
- In the "VIEW" column, click "Filters" then click the "+ ADD FILTER" button.
- On the "Edit Filter" screen, in the "Filter Name" field enter pa11y|sitemaster (the number one is typed twice, not the letter l). Under "Filter Type", select the "Custom" tab. Select the "Exclude" option. Under "Filter Field", select "Brower" in the dropdown. In the "Filter Pattern" field enter pa11y|sitemaster.