CSS Grid Generator is a website that allows you to create a grid from scratch then provides the CSS and HTML code to use within your code. The user has flexibility in mapping their rows, columns and gaps into grids with ease. This is the website that I used when learning about grids and found it very helpful.
Grid by example is a similar resource to css grid generator; however, it provides more information and explanations on how to use grid layouts. It includes examples, patterns, news and tutorials aimed at helping the user learn everything they need to develop a CSS grid layout.
The website classcentral.com in itself is not a great resource for users. It only redirects you to freecodecamp.org and other youtube videos to help develop CSS grids. I would not recommend using this site as it seems more like a blog post than a resource. Not enough useful information was provided except for links to other websites.
In conclusion, the most useful site that I reviewed is Grid by Example. It had more useful explanations than both classcentral.com and CSS Grid Generator combined. It was easy to use, easy to understand and the results provided working code in both HTML and CSS. I would highly recommend that all developers use this site to not only try to learn CSS grid layouts, but create effective code.