How to comment a single line?

Answer 1

In css, there's no single line comment format: you should use multiline /**/ comments even for a single or part of a line...
However, any unexpected character at begin of a line will result to disable the rule(s) standing on the line, but just because of syntax error (and you cannot be sure if next lines/rules would be correctly interpreted ;P)

Html also provide only one type of multiline comment <!-- -->

Anyway, in some coding, string litteral can form pseudo single line comments, as enquoted values without assignement are not necessarly syntaxic errors: this is at least true for Javascript and Python ^^

Answer 2

or you can do this # Python