ACTUALLY :
#orange is the ONLY clear syntax error.
the "$" is not an error at all, it just means "end of string"
The rest is valid CSS, but questionable LOGIC.
I would not assume the"." MIGHT be an error . The reasoning being ".a" is perfectly valid CSS, targeting class="a" but so is the "a" ( targeting anchor tags). Either could be intentional.
The space between the ".a" and "[" is also valid, especially if they meant ".a" as that targets any element with the href which ends in "about". this mean you could have a 4th level descendant anchor of a div with class ="a" and target it as shown in the question ( which leads me to believe that ".a" was intentional.
Even it if was "a [" and not ".a [" it's is still valid CSS, just pointless as only anchor tags may have the attribute HREF ( this would be an HTML validation error and not a CSS error), also you can't nest anchors so again it would be odd mean the anchor with the "href that end in about inside any other anchor"
a[href$="about"] {color:#cc3232;}
that is also valid CSS , but questionable logic. It is VERY VERY unlikely a file on the web will end in "about" as files must end in file types (".htlm", ".php", etc) So while valid, it may be quite useless.
if this was one of the choices, i would pick it instead :
Code:
a[ href^="about"] {color:#cc3232;}
"^" means strings begins with. so it would target "about.html", "about_us.php",etc.
$ just means "ends in" ,
Bookmarks