You can use the built-in "Find" feature in Firefox to search for specific text within an HTML file that is open in the browser. Here's how:

1)Open the HTML file in Firefox. 2)Press the "Ctrl" and "F" keys on your keyboard (or "Command" and "F" on a Mac) to open the "Find" bar at the bottom of the browser window. 3)Type the text you want to search for in the "Find" bar. 4)Press the "Enter" key on your keyboard to begin the search. Firefox will highlight any instances of the text within the HTML file. 5)Use the "Previous" and "Next" buttons in the "Find" bar to navigate through the different instances of the text within the file.

You can also use the "Find in This Page" option from the right-click menu in the browser to open the find bar and start searching.

You can also use keyboard shortcuts to navigate through the search results: 1)Press the "Ctrl" and "G" keys (or "Command" and "G" on a Mac) to go to the next search result. 2)Press the "Ctrl" and "Shift" and "G" keys (or "Command" and "Shift" and "G" on a Mac) to go to the previous search result.

Please note that these features may not be available if the HTML file is not loaded from a server, or if there are any other issues with the HTML file.

Thanks, Mich. I've copied your post to my "how to do it" list.