John,
If you want to get good data from your form, and you have two radio buttons, then neither should be checked by default. Your CGI script or whatever should do the checking and return the form with "you must select a button to proceed".
the difference between a radio button set and checkboxes is (going way back to Mac UI guidelines in the 80s) is that a radio button group always has a value, and the values are mutually exclusive (you can't check two radio buttons in the same group), whereas checkboxes in a group can all be on, all be off, or any combination of on and off. It's a long time since I have done some intensive forms work, but IIRC, browsers generally managed this for you if you set up your radio button sets properly.
I know, its strictly off topic, but its about conventions, which are a kind of standard
john
John Allsopp
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