For eight months my whole growth plan was "pour money into ads, fix conversion later." Conversion never got fixed because I never understood why it was broken. Here's the number that ended that era. I finally wired up basic event tracking and looked at what my last 100 signups actually did. 71 of them never once completed the core action the product exists for. They signed up, clicked around for three or four minutes, hit some wall I couldn't see, and left. I wasn't losing customers....