Source Code Editor
In order to create code for a webpage, you will need a special program called a source code editor. Sounds technical and fancy but it is an application like Microsoft word or Apple pages but is designed to help you code well. You can in fact write code in a simple text editor like notepad which comes with windows.
I recommend Notepad++ (http://notepad-plus-plus.org/) if you are using Windows or TextWrangler (http://www.barebones.com/products/textwrangler/download.html) if you are using an Apple Mac. Both are very similar and are free.
After you start the editor, create a new document and save it as index.html. Save the file to a location on your computer where you can find it. Browse to the location where the file is located using Windows Explorer on Windows or Finder on the Apple Mac. Right click on the file and select Open with a browser such as Google Chrome or Safari. Your webpage, although very empty for now should open in the browser. As you make and save changes in the source editor, refresh the page to see the changes.
The browser is a client application. Client generally means a computer application which a person interacts with. There are numerous browsers available including Safari, Internet Explorer, Firefox, Chrome and Opera being a few. Google Chrome is very useful for programmers like you as it provides tools which you will use to check your code. Google Chrome is available for both Windows and Apple Mac at https://www.google.com/chrome/browser/.