When is it best to just use CSS3 vs. Javascript? Is it a waste of time learning javascript since CSS3 can do so much?
They are 2 different beasts. CSS is a language of styling and Javascript is client-side programming. If you are strictly talking in terms of simple animation like a menu, learn CSS, but try to understand Javascript because there are a lot of menus that use effects, or libraries like JQuery which are Javascript based and you can never learn too much.
I think that depends on a) your project and b) target audience. Older browsers don't support all the cool new CSS3 properties.
If it's just for eye candy, probably not an issue. But if it effects usability (being able to see hidden content, for example), then JavaScript alone or in combination with CSS is usually a better choice.
Nancy O.
I agree with SnakEyez, with an addition. Learn JavaScript before learning any of the libraries (jQuery, MooTools, etc.), and definitely learn a library or two, but don't become dependent upon libraries.
For example: AJaX requests. Learn how to write out XHRs and use them - THEN, learn how to do it via jQuery. jQuery makes it simple (one line of code), but it's always a good idea to understand the process.
^_^
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