The network is currently moving forward at an enormous rate. Big drivers are Google, Yahoo and Facebook. See what they use and how they stay productive.
Today you should know how AJAX works, if you have been in the web business in, say, the last decade and have not yet encountered AJAX, it should at least become "aha," how it should have started " feeling for you.
Secondly, browser compatibility. First there was Mosaic, then Netscape ruled for several years. Then we had a war and Netscape lost it, mainly because of a bad strategy .
For several years (2000-2005) IE was the browser of first choice, where NS 4.7 was the defacto standard for compatibility with Mac, Linux, etc. These years were terrible (tables in tables in tables and 1x1.gif, etc.), but then Firefox appeared, Opera attracted attention, and now we have Firefox, Chrome, Opera and Safarai as quite worthy alternatives to IE.
To stay compatible with most browsers today, use jQuery especially to watch the full presentation “DOM is a mess” by John Resig, author of JQuery (google it yourself, I won’t advertise any particular video site). But there are alternatives, Dojo, YUI, etc.
On the server side, everything happens, especially in the field of new outgoing languages. Check out commonjs , node js , Couch DB
When millions of concurrent AJAX requests go through the network from millions of users of interactive interactive web applications, you cannot work with downloadable gigabyte weblogic or websphere server solutions, you must use lightweight server systems that easily scale for multiple servers.
One of the common factors both on the client side and on the server side is that JavaScript is becoming more and more acceptable. You must learn to write good JavaScript code, although you don't take Crockford's words too literally.
One nice thing on the Internet is that most of the knowledge is still as relevant today as it was said 10 years ago, the difference is that the workflow today has become much more productive.