When you begin a new search, the cursor is located in the Search Entry Box, and the Search History Box is blank. Clear the search and begin again by pressing F8. There are two ways of entering searches. The first, and most straightforward, simply uses key words to locate items of interest.
Search strings are case-insensitive.
You may build a search using any number of search strings. This activates the search, and presents a search status box indicating that the search is proceeding and reporting on the number of hits found. To terminate a search in progress, press Escape. This will end the search but preserve the hits located to that point. If you have the Reference edition, you can use the Index menu to browse index terms and add them to your search.