Question

Code for the below test: http://jsfiddle.net/fXdjm/

Questions about line heights:

• Please refer first box.What will be length of the distance between
  red border and the text top(say head of L) of the first line(“Gg –
  First Line”)?

• Please refer second box.What will be length of the distance between
  head of “S” in “Second” and head of “l” in “normal height”?

By the term head of “a character”, i refer to the top of that character. This is because, a line may contain tall and small characters like “lg”

Answer 1

Take a look at http://www.slideshare.net/maxdesign/line-height. The distance between the top of the G and the S (capital letters) is approximately the line-height minus the font-size / 2.

Here is some more explanation:

Content area
The font-size determines the content area which includes the area for capital letters and lowercase letters such as p,g, etc.

Leading
Line-height minus the font-size is called the leading

Half-leading
Space between top of capitals and the top of the box is called the half-leading.

This simple formula generally holds, however in cases where the line-height is smaller than the font-size it doesn’t!