A "×" symbol (a cross) in a box, as shown in "☒". If your computer displays something like a question mark or an empty box instead, then you have a font problem or very old browser.
Note that you may insert the symbol "☒" which is the Unicode character (U+2612). To do so:
- type ☒ or ☒
- You can also create a cross in a box like this ✘ using the following code:
<big style="border: solid grey 1px; padding: 0px 2px;">✘</big>