It sounds to like you want to learn while creating a web site. There are many platforms out there that are known as IDE’s (Integrated Development Environment). Be very careful when selecting an IDE as many people choose word processors such as MS Word. Word Processors use formatted text and your gibberish when you run it in a browser.
As far as IDE’s go, Dreamweaver will be the simplest as you can see a graphical representation of your work. The down side is it is very expensive. Aptana Studio would be a good second choice and it’s free. Sublime text is very good for editing just code and there is also notepad++
My personal favorite is Net beans. It may be a little heavy on your system because it requires you to install JDK(Java development kit). But if you want an IDE that does it all I would look into this one.
Also, another consideration may be older versions of Dreamweaver can be good to practice with. They will not bog down your processor as much. The functionality will bill not be as strong but it may be worth it until you learn basic coding rules. Bearing in mind that you loose the HTML5 and CSS3 code hinting.
Anymore questions, please don’t hesitate to ask,