The web is moving forward at a tremendeous speed nowadays. The big
drivers are Google, Yahoo and Facebook. Look what they are using and
how they stay productive.
As of today you must know how AJAX works, if you have been in the
web business for say the last decade and not encountered AJAX yet, it
should at least become a "aha this is how it should have worked from
the beginning" feeling for you.
Secondly, browser compatibility. First there was Mosaic, then Netscape
ruled the world for several years. Then we had the browser war
and Netscape lost it,
mainly due to bad strategy.
For several years (2000-2005) IE was the first choice browser, where
NS 4.7 was the defacto standard for compatibility with Mac, Linux
etc. These years were terrible (Tables in tables in tabels and 1x1.gif
etc...) but then Firefox arrived, Opera gained attention and now we
have Firefox, Chrome, Opera and Safarai as fully worthy alternatives
to IE.
To stay compatible with most browsers today, use JQuery
especially watch the full presentation "The DOM
is a mess" by John Resig the author of JQuery (google it yourself, I
wont promote any specific video site). But there are alternatives as well, Dojo, YUI etc.
On the server side, things are happening as well, especially in the
field of new exiting langauges. Check out commonjs,
node js, Couch DB
When millions of simultanous AJAX requests are flowing through the
network from millions of users of real-time interactive
web applications, you cant really work with gigabyte loaded weblogic or
websphere server solutions, you must use lightweight server systems
that scale easily to multiple servers.
One common factor in both client and server side is that JavaScript is gaining more and more acceptance. You should learn how to write good JavaScript code, although don't take Crockfords words too literally.
One nice thing with the web is that most knowledge is still as valid today as it was say 10 years ago, the difference is that the workflow today has become so much more productive.