When does reflow happen in a DOM environment?

Question

What kinds of activities will trigger reflow of web page with DOM?

It seems there are different points of view. According to http://www.nczonline.net/blog/2009/02/03

Answer 1

Look at the "Rendering triggered by Property Read Access" section of Understanding Internet Explorer Rendering Behaviour, where the following code in IE will cause rendering activity.

function askforHeight () {
  $("#lower").height();  
}