Type markdown (**bold**, # heading, https://news.com) — it styles live as you go and links open on click.
isposs saves your notes as a real isposs.md file on disk. Browsers need you to pick where to keep it once (a security thing — sites can't write to your disk without permission). After that, no more setup: every keystroke updates the file, and any external edits sync back into here.
Save it in a folder that syncs via iCloud/Dropbox if you want it on every device. Bookmark this page or install as an app from the address bar to return easily.