Totally agree with Louis-Philippe Breton. JavaScript is a great first language, especially if you follow some easy guidelines:
(1) JavaScript didn't come out a heavily peer-reviewed, academic or (until recently) standards-based environment, so it has some quirks. Learn the good stuff, and navigate around the not-as-good stuff (you don't need it). Our book (Head First JavaScript Programming -- not to be confused with Head First JavaScript) teaches from this perspective, and if you really want a long treatment of the good/bad take a look at Douglas Crockford's book "JavaScript: the good parts".
(2) JavaScript gives you a great environment to play in (the browser), that said, knowing HTML & CSS will help you do more interesting things with you JavaScript. So learn them in this order (HTML&CSS->JS), or concurrently.
(3) Don't get too married to the browser environment, JavaScript is a language useful beyond the browser, and you're going to want to understand languages down the road that aren't browser centric.
(4) Start simple--this is the real advantage of JavaScript (and why it's so popular), you can start very easily. And grow your knowledge from there. Start with variables, iteration, conditionals, and then move on to collections (arrays, etc.), then simple objects, simple functions. At that point you can start to move on to advanced topics like event-based programming, object construction and orientation and high-order functions/closures.
(5) Try not to get hooked on libraries too early. Work with the bare technology and understand it, and then you'll truly understand the libraries you're using, and how to best use them.
Hope this helps...
Eric