Hi Stu,
Take a look at..
http://www.w3schools.com/
It will give you the low down on HTML, XHTML etc, and will also provide you with an introduction to ASP so you can start playing around with forms processing and dynamic content.
To be marketable in this day and age you should be capable of turning your hand to anything in the "web development" domain. I suggest that you will need to get your hands dirty with a programming language, such as Java, and grasp an understanding of relational databases and SQL. I'm sure this will be disputed by some of the more design-oriented web folks who may never need to know this, but in the long run you will be doing yourself a favour if you can at least talk shop with some of the more "techie" members of your team.
As advised before, have a look into JavaServerPages (JSP), the Java way of providing dynamic pages, and also have a look at JSTL (JSP Standard Tag Library) . The JSTL wraps up a lot of common functionalities like database access and output formatting, and is designed to be used by web page developers. It's usage does not require you to be an expert Java developer, however a comprehension of Java web technologies is essential if you are to become a "JSTL guru".
As far as software is concerned, there are numerous free (open-source) servers and databases out there that you can downlaod and play around on, and there are lots of tutorials to work through.
Good luck and PM me if you want any further info.
???pax