Forced to load an Add-on I do not want

I am trying to open a site, but keep getting this message: "Before you continue to the website...

By clicking the "Accept and Continue" button, you will be redirected to the Firefox Add-ons Store to install this extension. By clicking the "Accept and Continue" button and installing this extension in your browser, you accept the Terms and Conditions, Privacy Policy, and agree to select "Recipio" as your new search engine. Firefox Add-ons Accept and Continue" I do not want to add it - why am I being forced to add it?