Font sizes for different header levels

First of all, under an 11pt document class option, you need to know the different font sizes associated with the font switching commands. Either examine size11.clo, or see What point (pt) font size are Large etc.?

The rest can be taken directly from report.cls:

• chapter; examine @makechapterhead (or the starred equivalent @makeschapterhead):

  • Space before: 50pt to Chapter X; 20pt between Chapter X and title
  • Font: hugebfseries = 20.74pt
  • Space after: 40pt

• section; examine the parameters passed to @startsection:

  • Space before: 3.5ex ~ 16.5pt
  • Font: Largebfseries = 14.4pt
  • Space after: 2.3ex ~ 10.8pt

• subsection; examine the parameters passed to @startsection:

  • Space before: 3.25ex ~ 15.3pt
  • Font: largebfseries = 12pt
  • Space after: 1.5ex ~ 7.1pt

• subsubsection; examine the parameters passed to @startsection:

  • Space before: 3.25ex ~ 15.3pt
  • Font: normalsizebfseries = 11pt
  • Space after: 1.5ex ` 7.1pt

• Regular paragraph

  • Space before: parskip = 0pt
  • Font: normalsize = 11pt
  • Space after: parskip = 0pt

LaTeX does provide paragraph and subparagraph headings, but they are rarely used.

Note that LaTeX's headings have some rubber lengths built in, meaning the length may vary slightly, depending on the actual page content. However, this is of no concern for websites.