If you have accessibility needs and must use a computer keyboard instead of a mouse, you might rely on using the Tab key on your computer to move about the page. Website designers should build and test for this. Sometimes you might find that the behavior of certain browsers is different from others. Tabbing might work on Chrome but not on Firefox.
If you are on a Mac, it might not be the fault of the browser. There is a setting in
System Preferences >> Keyboard >> Shortcuts
at the very bottom of the page called Full Keyboard Access
Make sure this is set to All Controls.
Type about:config in the address bar, and Enter.
Type tabfocus in the search at top of the page.
You likely want accessibility.tabfocus given a numerical value of 7.