To search inside a Web page, in the menu bar, click Edit › Find or press Ctrl–F. The find bar opens. It is usually displayed at the bottom of a window. Type your query in the text box. Firefox finds the first occurrence of this phrase as you type. You can find other occurrences of the phrase by pressing F3 or the Next button in the find bar. Clicking the Highlight All button will highlight all occurrences of the phrase. Checking the Match Case option makes the query case-sensitive.
Firefox also offers two quick-find options. Click anywhere you like to start a search on a Web page, type the key / immediately followed by the search term. The first occurrence of the search term will be highlighted as you type. Use F3 to find the next occurrence. It is also possible to limit quick-find to links only. This search option is available by typing the key '.