I do all of my web development in Notepad++, which is an open-source (and thus, free) alternative to Notepad. It has built-in syntax highlighting for many, many different languages and all the nice little perks of any coding IDE.
To make a website, you'll definitely need to learn HTML. HTML is the markup that browsers read in order to render a page, there is no alternative. I also highly recommend learning about cascading style sheets (CSS), which lets you set the design for your entire site in one page.
HTML should be used to define the structure of a page, while CSS is used to define style. JavaScript will enable you to create user-interactive websites, while PHP (alongside a database, such as MySQL) will provide for more advanced server-side scripting such as forums and user/login systems.
You can learn about everything you need to know at W3Schools.com.