Install this bookmarklet into your browser by dragging it to the Bookmarks Bar.
Then, whenever you are on a page that you find interesting, click on the "Webnote It" bookmarklet. Webnote will appear, with a new webnote for the page that you are on. You can then type in a note.
If there is already a webnote for the page, then Webnote will take you to the existing webnote, so you can view it. This is a good way to see the notes that you took the page.