Sometimes the URLs you're testing change. You might not care if you lose all the previous test data, but if you'd like to keep the old data and be able to compare it to the new test results, read this article.
Edit a URL and keep your historical data
It's possible to edit a URL that belongs to a site and preserve the historical data for the old URL. To do this, simply edit the URL and save your changes. You might want to add a note to your site to mark the change. (Go to your Settings page and scroll down to the Notes section.)
Delete a URL and its historical data
To delete a URL and its historical data, simply delete the URL using the "x" icon at the end of the URL field. When you delete a URL its historical data is also removed. There's no way to recover this data, so make sure you only delete a URL when you no longer need the data.
Remove historical data and add a new URL
If you don't care about the old test data and just want to add a new URL, then delete the old URL. Once the old URL is removed, click "Add URL" to add the new URL. This deletes all the old test data and starts the new URL off on a clean slate.
Keep historical data but stop testing
You can pause testing on a site by site basis. Simply edit a site and then uncheck all the scheduled test times.