W3SCHOOLS
everyone and their nana uses w3schools but i cannot stress how much its helped me! i basically learned how 2 code from w3schools
DYNAMICDRIVE
lots of css and html effects here! really good website 2 use for spicing up ur page
JAVASCRIPT BEST CODES
a website similar to dynamicdrive, i dont use this one too often tbh
PAGETUTOR
this ones a little ad-heavy but its another html, css and javascript tutorial site.
JAVASCRIPT KIT
self explanitory name.
CSS TRICKS
this one's probably my favorite, theres a whole load of indepth CSS tutorials here. This website looks more modern than the rest too, i really like the way its structured.
STACKOVERFLOW
an excellent website where you can ask questions about code and get quick feedback, if anything ever goes wrong with ur code stackoverflow is the place to go to!