Firefox has a search option for finding text on a given a web page. This search option can be launched either by the keyboard shortcut (Ctrl + F) or by navigating to Edit menu and selecting Find from the available menu list.
The search option gets displayed at the bottom of the browser window as shown below.
Type the text you want to search on the text field available next to the label Find: and click Next. This would highlight the entered text if it is present in the current web page otherwise it will display Phrase not found message. If you want to continue searching the same text, then again click the Next button. By selecting Highlight all option, all the occurrence of the search text in the web page would be highlighted as shown below.
By default the search available in Firefox displays both uppercase and lowercase matches. if you want to Match text by case, then mark the checkbox with label as Match case. To close the search option click the X mark available before the Find: label.