Occasionally, I need to group select content. In the past, I used program control. Today I found that there is an optgroup attribute in select that can be used.
It has been tested and suitable for browsers such as Firefox and IE. The only shortcoming found so far is that the title style after the group cannot be customized. For example: If you want to change the font attributes, you cannot use a normal font, but you can change the color and size. The default under IE is italics and bold