When importing a new template into the builder, be aware that some developer might specify that the width and height of the body is 100%. There is nothing necessarily wrong with this, however, by default the width of the body tag is 100% and the height is dictated by the content inside the body. When specifying the height as 100%, the builder might not be able to assess the real height of the body, since the content is no longer taken into consideration.
/* avoid */
body {
width: 100%;
height: 100%;
}