Below are the step-by-step instructions on how to increase the text size in Opera 8 for OS X
Unlike in Internet Explorer and Netscape Navigator, Opera can increase the size of images as well as text.
You can quickly increase or decrease the size of both text and graphics using the numberpad ' + ' (or ' 0 ' ) and ' - ' (or ' 9 ' ) keys. Each press will increase or decrease the size by 10%. However these changes will not be remembered next time you open Opera.

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Note: If this does not work it could be because your computer settings cannot be changed due to local IT policies - contact your local IT support for further help.