You can build many useful web apps with just a few files. You can also extend this simple notes app to add more functionality ...

SimpleNote, just like the name implies, is a simple, basic note taking application/service. It’s just about text notes. No images. No voice notes.

Just like any chat app, you can start typing and hit “send” to write a note or a thought. There is a handy checkmark sign above the textbox, so you can easily create a checklist or a to-do list.

It's very simple, but if you want your note-taking app to act like a sheet of scratch paper on your desk, and not a full-fledged tool, Squarespace Note is worth a look.