HTML Tip: Sorting With The OPTGROUP Element: I found a tag today that I had never heard of before. OPTGROUP allows you to have an option in a dropdown that isn’t selectable, is seperately formattable via CSS, and that other options are indented under.
Until recently, the OPTGROUP element belonged to that lonely category of valid HTML tags that most major browsers didn’t recognize. Fortunately, Netscape 6.x and Explorer 6.0 for Windows have joined Explorer 5.0/Mac in supporting this handy way to categorize SELECT lists. […]
…OPTGROUP is low-impact. Older browsers just ignore the element and display a regular SELECT list.
Visit the page to see a screencap. Apparently IE 5.0 for Mac is the only browser that supports it to the extent called for in the spec, essentially creating collapsible flyout menus. Very, very handy.