Opera users:

To change the text size:

• Click on 'File' in the top menu toolbar.
• Click on Preferences, then (in the left-hand 'Category' section of the dialogue box) 'Documents'.
• Specify the font-size you require in the 'Minimum font size ( pixels)' option.

Help from the Opera site:

• See Visual impairments and Opera
• See Mobility impairments and Opera
• See Accessibility in Opera