To change the observing mode of a bookmark:

Choose Bookmarks > Set Update Mode in the menu or in the context menu of the bookmarks.

Select the observing mode for the selected bookmarks.
Manual: Webbla will not observe the website automatically. You must check for changes manually by pressing the reload button.
Once per Session: Webbla will check the website each time you start Webbla. If you have many bookmarks and Webbla is not be able to check all in one session, Webbla will continue to check the unchecked bookmarks at the next time.
Continuously: Webbla will check the website continuously.