html - Styling the placeholder of an input, how can I do this?

no standard way, and not every browser supports place
holder yet.

Something like this should do
it.:

/* prefix with input if you want, but
            this will catch input and texatrea */
 ::-webkit-input-placeholder { color:
            #000;}
 :-moz-placeholder { color: #000;
            }

href="http://jsfiddle.net/CHG46/"
rel="noreferrer">http://jsfiddle.net/CHG46/

if
you want old and new browsers to support placeholder (IE6-9) there appears to be a
jquery plugin(s), here is one,
href="https://github.com/mathiasbynens/Placeholder-jQuery-Plugin"
rel="noreferrer">https://github.com/mathiasbynens/Placeholder-jQuery-Plugin
however,
I have not used it before.