what's the name for an HTML SELECT control's visible portion?

I've looked far and wide, 开发者_如何学Gobut could not find anything.

Is there an "anatomy of HTML elements" guide of sorts that has this kind of information?

EDIT: By "visible" I mean "visible by default", without user (or anything else for that matter) having engaged it.

"the dropdown (arrow|icon|button)" is the name of the thing on the right side and "selected value display" is the (usually) white box with the default/selected value. As far as I know, there are no standard names for the shadow dom

I would call this "selected value". In ASP.Net, for example, that's the property name for the visible value in a drop down list control (a SELECT input).

If, by visible portion, you mean 'What option is visible by default (or on the initial load)", what you need to do is add 'selected="selected"' to the option tag you want to show eg:

<select name="tester">
    <option value="1">First Option</option>
    <option value="2">Second Option</option>
    <option value="3" selected="selected">Third Option</option>
    <option value="4">Fourth Option</option>
</select>

This would display a select box with 'Third Option' showing in it.

You can find out more about <select> and <option> on W3 Schools:
http://www.w3schools.com/tags/tag_select.asp
http://www.w3schools.com/tags/tag_option.asp

Are you referring to the CSS display property? Also might help to understand what you are trying to accomplish.