I do agree you should start to get everything written down. Open up a Google doc, email, pen&paper, whatever- and start writing. Stay away from making everyth

I do agree you should start to get everything written down. Open up a Google doc, email, pen&paper, whatever- and start writing. Stay away from making everything detailed though. Your ideas will change, you do not want to invest all this time in "formalizing every aspect of the webapp". There is no way you can even begin to foresee every single aspect. Instead, invest that time creating/building the webapp. Build the home page, make some images, start writing code. Reference what you've written down and be prepared to change/edit/redo your notes. Once you get some working examples/demos/mockups then start to use more traditional formalizing software. A ticket system for features/bugs, or maybe a spiffy project tool for notes/todo. Whatever floats your boat.