Something I discovered, be careful copying and pasting Glenn’s example above. The CSS editor doesn’t like the inverted commas after content: . At least, Chrome doesn’t. They paste as curly, whereas typing them, they’re straight.
Actually, on closer inspection it looks like it was a combination of the inverted commas and a period:
Take the period out, or change the commas and it’s fine.
.transform-invTypeName1 {
content: "MY NEW LABEL"
}
You will often find that copying directly from forums and webpages in general will also copy things you don’t want so it’s always worth pasting into a text editor first to clear any lingering formatting and special characters.