Reading text that is too small for prolonged periods of time strains the eyes, and many users have difficulty seeing.
Increase Text Size System-Wide (Windows)
To adjust font size in Microsoft Windows, open the control panel and double-click the Display icon. If you do not see the display icon, click "Switch to Classic View" in the left sidebar. In the Display window, click the Settings tab. Choose Advanced. Under the General tab (the first one that comes up), switch the DPI from 90 to 120. Click OK. Now click the Appearance tab. Click Effects. Check "Use the following method to smooth the edges of screen fonts" and choose "ClearType". If desired, one can also check "Use large icons" here. Click OK. As a final increase, one can select "Large fonts" or "Extra large fonts" from the drop-down menu on the Appearance tab.
Adjusting Text Size on the Internet (Mozilla Firefox)
Mozilla Firefox is perhaps the easiest of the major browsers to dynamically adjust font size while reading pages. Because of the many websites that disregard standards, dynamic font size adjustment is very useful since some pages will appear to have very small text and others very large. To increase the text size of the pages you are viewing, hold down the CTRL key and press "+". To decrease the text size, hold down the CTRL key and press "-". This works on both PCs and Macs.