For purpose of example I've got a single cell table (the actual table is bigger) with a picture in it. And when I add the doctype code, space is added to the bottom of the cell. I think adding the doctype code is a good idea but I don't want the space at the bottom.
How do I remove the space?
Below are two sets of code. They're both the same except the second one has the doctype added and this creates a space at the bottom of the cell.
The doctype puts the document into standards mode instead of quirks mode, so the <img> (an inline element) is automatically aligned to the text baseline of the table cell instead of the bottom. That positioning leaves the extra space below for the "descenders" that fonts need for some letters.