I have a table and at some rows i want to place the td at the end of the row

I’m using rowspan on a HTML table with varying rows, however I’m experiencing an inconsistent cell height as screenshot. I would expect each cell to be evenly spaced, exactly like the row above – am I missing something or is this a quirk?

In the following example, the offsetTop of tr rows in a table returns different results for Firefox and Chrome(Brave version) when a td within the tr has a border top and bottom.

I am trying to create a table with colspan and rowspan inside.