In the screenshot of TextMate below, I turned on "Show Invisibles." What's the whitespace character on the third line?
Text I imported from somewhere has these dot spaces, and I'm trying to figure out what they are.
These are non-breaking spaces.
In contrast to normal spaces, they won't cause a line break. For example, you may want to add one between "OS" and "X" when you write "OS X". In HTML, they're created through the
To inspect them, just copy them to Character Viewer's search box (press ⌥⌘T):
Whether you want them or not depends on your application. Some compilers might chocke on these non-ASCII characters, for example. It's generally better to replace them with normal spaces unless you really need them.