A tick ("check" in American English) symbol 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+2611). 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 1px;">✓</big>