I have a table inside a div with a background. I would like to add a cell with the sum of all values in a column, pasted as an extra cell to the bottom of the table at the right side (the right column is the column with numbers). This should happen without my preceding column cells removing my background. For clarity I have added a picture of an example template.
Now my question is, does there exist a HTML predefined tag or option to add just one cell at the right of a row, or would I have to style a preceding td tag with colspan=3 with transparent background, no borders etc… to get this result.
The answer to your specific question is no. There is no way to create a table that is not a perfect rectangle. But you can, as other have pointed out, style a table to get your desired look.