user: Question: What percentage of users were using Netscape during the period in which 21.67% were using Firefox?
Columns: ['Period', 'Internet Explorer', 'Firefox', 'Safari', 'Opera', 'Netscape', 'Other Mozilla']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['2011 Q2', '54.36%', '21.67%', '7.30%', '1.97%', '0.79%', '0.03%']
SQL:

assistant: SELECT "Netscape" FROM "Table" WHERE "Firefox" = '21.67%';