The browser could care less. You could write your pages in one straight line and it would look the same. I would suggest you do it only to keep it all straight when you look at the document.
Jake Young writes:
I don't know how many versions of Netscape have the following bug: for images in a table the <img> tag must be on the same line as the <td> and </td> or else there will be space above and below the image.