You can search for text across all of your documents by using the search box located in the show bar:

To search, simply type one or more words into the search box and click on the Search button . Results are instantly displayed. To clear the search, click on the
that appears next to the Search box.
Note: the search box always searches for the exact full text you type; e.g., if you type 'red cars' it will only find documents with 'red cars', not also documents that have only the word 'red' and documents that have only the word 'cars'.
When you are viewing or editing one particular document, you can search for text within that document by using your browser's find command. In both Firefox and IE, go to the Edit menu and choose the Find command (or use Ctrl-F to instantly open the find command).