If nothing has happened to the content since last year and the browser is the same most likely you have altered the browser preferences, for example zoomed the page or altered the advanced Fonts settings.
I have to agree with Robert on this one. It sounds like a local browser issue rather than a web site/server issue. The screen shots appear to show the same font with different sizes.
Is the text-only zoomed (magnified) in Firefox? If so, View > Zoom > Reset should restore your browser defaults.
In Firefox, you can set your browser’s default font and font-size here: Tools > Options > Content