For those of us, um, you over forty that have a hard time reading that minute, usually sans-serif text on web-pages...
In Internet Explorer, you'll ususally be told to go to View>Text Size to change font size. But that's a lot of clicking if you need to adjust it just right. And on some pages, text lines viewed with a large font size will bleed over one another and appear to be a confusing jumble. These need to be changed temporarily to a smaller font size. Here is a quicker way if you have a mouse with a scroll wheel that supports this.
Hold down the Ctrl key while rolling the scroll wheel & watch the text size change as the wheel turns.
This can also be done in Mozilla, but it has to be set up first. In Mozilla 1.6 (don't know about Firefox but it is probably the same) go to Edit>Preferences>Advanced>Mouse Wheel>Control tab>Make the text larger or smaller.