Lavashark's right. Everything you write is automatically copyrighted to you (unless you've signed those rights away, as in a work for hire), whether it's web content or a personal letter.
See
http://www.whatiscopyright.org/ : "If it is an essay, if it is a play, if it is a song, if it is a funky original dance move, if it is a photograph, HTML coding or a computer graphic that can be set on paper, recorded on tape or saved to a hard drive...copyright protection begins when any of the above described work is actually created and fixed in a tangible form."
This site isn't ENTIRELY correct (a funky dance move is probably not copyright-able, and neither, by the way, is uncompiled code), but you get the idea.