<html><head><style> input:checked{background:#ff0000;}</style></head><body><form action=""><input type="radio" checked="checked" value="male" name="gender" /> Male<br><input type="radio" value="female" name="gender" /> Female<br><input type="checkbox" checked="checked" value="Bike" /> I have a bike<br><input type="checkbox" value="Car" /> I have a car </form><p><b>注释：</b>本例只在 Opera 中正确地工作！</p></body></html>