You must test the actual ads or landing pages. Do not rely on the Ad Preview tool!
In this article we’ll demonstrate a problem that can be caused by Google’s Adwords Auto-tagging, which is turned on by default when you create an AdWords account. Auto-tagging can cause some landing pages to load incorrectly, often resulting a “Page Not Found” error, – Wasting many dollars in Adwords Click charges and missed business opportunities. We demonstrate the issue in a 4 minute video, show you how to test for problems, and suggest what to do if you have problems.