Easily Identify Collection & Block IDs for CSS
Finding out Collection and Block IDs can be a real pain, but with this tip, you'll save yourself a lot of time and effort. What you'll need to do is download and install a Chrome extension called "Squarespace Collection/Block Identifier" from the Chrome Web Store.
Note that this only works in the Chrome web browser, not with Safari or Firefox.
Once you get the extension installed, all you have to do is click the extension icon when you're on any Squarespace page. The ID's will appear on top of each block. If you click on the ID #, it will automatically copy to your clipboard. That's it!