Several month ago, someone ask me how to study about web. She already had heard about it like designing web or put a good user interface in the web but she is still confused how to understand web well.
Basic skill to make a web site
First she need to understand the HTML/XHTML. She should try to make a HTML document from simple to advanced. She needs to know to build basic layout of the document.
Then she needs to give a good style to the HTML through CSS. She can give color or maybe give margin to the layout so the web site looks good.
To make a page more responsive and interactive it needs a client script like javascript and DOM. The scripting provides client side programming and DOM provides the document model that the script manipulates.
After that you need to test it with many browsers. I recomendate use Internet Explorer and Mozilla Firefox as a standard for testing. Other browsers are OK. It is needed to look at result in the different browser.
Basic internet knowledge such as using FTP or browser needed to do some basic web hosting management. These are important for uploading files, managing folders and setting up environtment on the hosting site.