The letter “X” is not a multiplication symbol. Not in its uppercase form, and not in its lowercase form, either. The multiplication sign looks like this: ×
A superscript letter “O” is not a degree sign. A degree looks like this: °
A lowercase “u” is not lowercase Greek letter mu, better known as the metric symbol for “micro-”. The micro- symbol looks like this: µ
And we can tell the difference.
If you use Microsoft Office, here’s the part of the ribbon you’re looking for:
Windows users can also open up the Character Map for even more symbols.
One major technical symbol that is missing, and which scientists often want to use, is the mean symbol. It looks like an x with a bar over the top. For some reason, the mean symbol is not in Unicode character sets, or in HTML, as far as I can find.
I have seen these kinds of mistakes in documents, and slides, and posters, many times.
These mistakes show that you don’t know how to use your tools. That is the definition of amateur. And wouldn’t you rather look like a professional than an amateur?