I have been studying HTML and CSS for about a month and working on creating a homepage. However, I felt the limitations in the design aspect and while searching, I found out about Bootstrap. When I tried to use Bootstrap, it felt like I was learning something new, different from the CSS I had studied before. So I looked for a lecture. After listening to the teacher's lecture, my understanding greatly increased and I was able to use it properly. Thank you very much. The following are questions and opinions. ======================================= This is about web standards. After proceeding with the project, when I checked the HTML on the validation site https://validator.w3.org/ all the width parts in the class were errors. Of course, there is no problem using the site even if there is an error, but I wonder if this error is a problem in terms of web standards. For example, when I was hired at a company and was instructed to create a website that conforms to web standards, this part was about whether this part was a problem. When I deleted the part that caused the error and wrote it directly in the css file, the error part disappeared. I don't know why, but the location was slightly different when it was written in the class and when it was written in the css. I was able to fix that by modifying the col value. (In the 3 columns of the navbar designated as col-3 col-5 col-4, the logo in col-5 was shifted to the left, By changing it to col-4 col-4 col-4, the logo was centered.) If this part is a problem with web standards, I think it would be better for the teacher to teach in the direction of writing in css from the beginning, so I am cautiously suggesting my opinion. It's not a question of right or wrong, but just a question about something I'm curious about, so I hope you won't be offended. The following are my opinions about the following lectures. ===================================== Before I listened to your lecture, I used several templates on the Internet, but when I actually applied them, they didn't look the way I wanted. Based on my limited knowledge, I think the versions of Bootstrap are different, and the original creator of the template may have customized some parts other than the CSS provided by Bootstrap, so it may not work properly in my index file, which only has a CDN link. So what I suggest is, If you could tell me the process of creating a single webpage by using several versions of several templates, and pasting codes here and there, I think it would be a great help. (Depending on the version difference, this part of the original creator's code needs to be modified, and if the CSS doesn't work properly, how to analyze the code and modify it, etc.) I'll say thank you again, and I'll stop here.