When writing a question or answer there are some commonly used symbols or typesetting styles that are missing. The two that come to mind are the degree symbol (°) for temperatures and refractometer readings, and subscript (e.g. CO2) which often come up on the site.
I didn't know this before writing the question - to get the degree symbol, I googled and copy/pasted the symbol from text in the page. There's a much quicker way:
- degree is
- subscript is
<sub></sub>around the text. E.g.