This site offers a useful guide to making font sizes bigger and smaller – no matter what web browser you’re using. Here’s how you do it with your mouse or keyboard:
Tip: If you have a mouse with a wheel and are using any of the below browsers, you can increase and decrease the size of the fonts in your browser by holding down the Ctrl key and move the mouse wheel up or down. Alternatively, you can press down and hold the Ctrl key and press either the + (plus) or – (minus) keys on the top of the keyboard to increase and decrease the font.