There are many websites to help you learn HTML/CSS
Just doing a quick Bing search for 'online html tutorials' will show so many online resources to learn coding with HTML and CSS. I would say 80% of online material is free for coding lessons. Here are three of my favorite references/train sites I often go to and would recommend to others.
I believe this is the first page a came to when I was looking for some extra info on id's and class's. It helped out a lot with many explanations and examples. On some pages there are quite a few comments at the bottom of a lesson or article where I have also learned a lot. Maybe this is more of a reference for the more knowledgeable, but it has always had some 'tricks' that I started using.
I haven't spent much time on the computer at code academy but us it all the time of my phone. Their Android app is pretty good. Html and css coding are just a couple things available at this site. They have fairly thorough beginning guides for several programming languages(like Java, Python, JavaScript, jquery, C++, and more) I just found out about this site a week ago when I downloaded the app on my phone to help with my very limited JavaScript knowledge. I like there html and css as well, great for just starting out.
The Microsoft Virtual Academy has the most resources for free online that I have come across. I've listened to some of the CSS lessons and it was pretty good. There are several 'classes' that can take a long time to get through, but without moving slow. Their lessons are mostly videos, some articles. I wish the beginning programming language sources had more written content. That could be a good thing for some though. It was a benefit for me a few years ago when I started playing with C#, just never got all the way through one of their coursed(they can be long!) lasting for weeks or months when some might just want to do a little here and a little there.
I believe this is the first page a came to when I was looking for some extra info on id's and class's. It helped out a lot with many explanations and examples. On some pages there are quite a few comments at the bottom of a lesson or article where I have also learned a lot. Maybe this is more of a reference for the more knowledgeable, but it has always had some 'tricks' that I started using. 
I haven't spent much time on the computer at code academy but us it all the time of my phone. Their Android app is pretty good. Html and css coding are just a couple things available at this site. They have fairly thorough beginning guides for several programming languages(like Java, Python, JavaScript, jquery, C++, and more) I just found out about this site a week ago when I downloaded the app on my phone to help with my very limited JavaScript knowledge. I like there html and css as well, great for just starting out. 
The Microsoft Virtual Academy has the most resources for free online that I have come across. I've listened to some of the CSS lessons and it was pretty good. There are several 'classes' that can take a long time to get through, but without moving slow. Their lessons are mostly videos, some articles. I wish the beginning programming language sources had more written content. That could be a good thing for some though. It was a benefit for me a few years ago when I started playing with C#, just never got all the way through one of their coursed(they can be long!) lasting for weeks or months when some might just want to do a little here and a little there.