HTML, CSS, JavaScript, ASP, and ASP.NET
So how much do you REALLY need to know? Probably not a lot, if you're lucky. Most visual changes only need basic understanding of HTML, and any modern HTML editor should be able to recognize any existing ASP elements and work around them as you change the layout. A lot of benefits can come from adding JavaScript, such as a script to toggle some text on-and-off if a user clicks on Help, or a nice floater to reveal info for your users about how to feed in their domain credentials. ASP, however, is probably the most important thing here.
The ASP web-scripting interface and the VB language it uses are quite old, and a lot of people know them well, so we will not attempt to teach it here. Another key concept is Server-Side Include (SSI), which is also used a lot. Normally, you wouldn't have to change these, but if you need to add your own files, this can become tricky, because inclusions are very sensitive to folder hierarchy. Some parts of UAG were written using ASP.NET, which means you won't be able to edit them, and even reading the code will be quite limited. Cascading Style Sheets (CSS) is also important, as a lot of the look-and-feel of UAG is controlled this way. At the end of the chapter, we have included a list of books that may be a good start towards brushing up on these technologies.