I tried many suggestions to make tables - this answer details the best way I've found to add tables to Squarespace.
Custom Table Block
[Updated 2019] The best solution I have found for responsive and well designed tables on Squarespace is the Custom Table Block that can be purchased as a plugin. Once added, you can add tables just like other standard Squarespace blocks on any page. If your table contains more than a few rows/columns you can add your data to individual Google Sheets and then link them to a Table Block. It's by far the easiest way to add Tables to Squarespace.
Convert Table to HTML
If the customer already has the table in a Word document, I'll use the excellent free Word to HTML tool by Olly Cope. I paste in the table and it will convert it to HTML.
Create HTML Table
If I don't already have the table I will create it using the excellent HTML table generator at Tables Generator with the CSS option turned off.
Use a Code Block
When the HTML has been generated, I add it to a Code Block on the Squarespace page. I replace the initial
<table>
tag with the following:
<table class=mytable>
Add some Custom CSS
So that the table is formatted to match the style of the site I then add a few lines of CSS to the Custom CSS page. Something like:
.mytable {
border: 3px solid #5f102b;
background-color: white;
th {
padding: 6px;
height:40px;
color: #eeeeee;
background-color: #5f102b;
}
td {
padding: 6px;
border:1px solid #f1eaf2;
}
tr:nth-child(odd){background-color: #f1eaf2}
}