Here is a little hint to increase the overall font size for either the main site, the forum, or both.
At the top right of the page on the forum you will see the letter "A" surrounded by an up and down arrow. Click this to change the font size on the forum.
To alter the font size on the main site is very similar. At the top of the page on the main site you will see "A A A" Click on one of these to make the font size larger or smaller.