On the editing page for a person, two tabs separate the information -- "Main" for the vital information and "Notes" for other general notes. Anything that does not fit in elsewhere, feel free to enter here. There is practically no limit as to the amount that you can enter.
If you wish to put website links in the notes, just copy & paste the link, preferably including the http:// or ftp:// at the beginning. It should automatically be recognized and will link itself.
The Notes tab contains two notes fields -- one for text that is displayed for anyone browsing through the site, and second a more restricted notes field that displays only for people who are logged in and identified as a moderator or subscriber of the person in question.
In the second you might keep more speculative information about who someone's relatives might be,information about where they may have migrated to, theories you're working on, or other notes about leads you want to look into later -- anything you want to record for future reference, and collaborate on with other researchers, but don't want to put out there for the world to see.
The general search options do cover both notes fields, but results will return from the second notes field only where you have the ability to access the information. To search specifically the "Notes for Research" field, choose this option under the "Other Search Options" choices.
Choice of Notes Editors
One example of how you might use the more advanced formatting options is if you have a record where the person's information is in doubt, and you want emphasize this for people browsing. You can make the text bold red to make it easier to spot the warning.