It’s a basically because in Chrome, the intro H2 text “Going away for awhile and want your house and animals cared for? We offer short and long-term housesitting!” takes up only two lines, whereas in Firefox, it takes 3.
The quickest way to fix this is to give the .title a height of 190 pixels.
However, if you want to fix it properly, you’ll need to dig into the way the H1 and H2 are displayed. On Firefox it looks much heavier, not sure if you are OK with that or not.
Not everything has to look exactly the same in every browser, but you might want to give that a deeper look, regarding the font size/spacing/weight of those fonts.