If you make major design changes to your Weebly site, always make sure your tracking code is still installed.
Login to Darwin's Dashboard and visit "Tracking Code" in the navigation.
Copy the tracking code HTML that you'll find there.
Login to Weebly and go to "Settings" in your Weebly site's dashboard.
Click on "SEO" link from the left menu.
Add the tracking code in the "Header Code" text box and click save.
Click "Publish" button on the top right.
Once you've saved your changes, you can verify your install on the Darwin dashboard.