One thing I definitely needed to be able to do on Squarespace is properly format any source code I might have in a blog post.
I currently have one posted with code here. The Python code in the post is nicely formatted.
To do this, I followed the instructions at http://www.webmasterymadesimple.com/blog/displaying-formatted-source-code-in-a-squarespace-website.html For the most part I just followed the steps one by one, but there were a few wrinkles.
I'm going to write my own version of the steps. These essentially match the original article above, but I'll call-out when I had to do something different.
Step 1: Download the latest version of SyntaxHighlighter
This worked fine for me. At the time of writing, the latest version is 3.0.83
Step 2: Uploading the SyntaxHighlighter source
This didn't work quite right. The original post calls for creating a directory, and then uploading into directory. For me, that ended up creating too many directories in the hierarchy. Instead, I skipped creating my own directory and just uploaded syntaxhighlighter_3.0.83.zip into the root of my storage area, remembering to check the Decompress Zip Files After Uploading option.
Then I simply renamed the uncompressed directory from syntaxhighlighter_3.0.83 to syntaxhighlighter
Step 3: Configuring SyntaxHighlighter
Step 4: Turning on the SyntaxHighlighter
That's it for getting it installed properly. In terms of creating posts that use this feature, I'll refer you back to the original post, as all of his instructions there worked just fine for me. You only need to make sure that instead of brush: js you use brush: python