When we use the folder properties dialog box of Windows XP, we will find that the Read-only and Hidden options in the Attributes category of the folder are sometimes not completely checked or unchecked, but often a state where the background is gray even though it has been checked. In fact, this uncertain CheckBox state can also be expressed in the Web.
In the web page, we can use <input id=chkb type=CheckBox> to get a CheckBox control. The most common form of this control is checked (with a checked) or unchecked state. We use mouse clicks to easily switch these two states, and we can also use scripting languages to change their states, such as using JavaScript scripts:
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