This is very good tool to create you to do lists, important notes, save some credentials online.
This tool is just as using Microsoft word online, I found it even better than word. Everything is online and is very safe, its also a free to join program, you can also opt for premium features by paying.
Evernote has both website and mobile application, both the data are synchronized at real time.
The ui and usability of the website and the mobile application is just awesome, I highly recommend to use this tool.