On that page that asks to confirm MPG there are two options below the "Does this MPG value look correct?" - yes and no.
Below the yes answer there are options to add another fill-up, go to fill-up history, etc.
We have tested that page in latest versions of Firefox 2.0 and 3.0 and it appears that links are visible and clickable.
You may have to scroll your browser window to see them.
Please check if the issue is with scrolling and let us know.
Thank and have a great day.