Most designers know the value of white space, which is the empty space between paragraphs, pictures, buttons and other items on the page. White space de-clutters a page by giving items room to breathe. We can also group items together by decreasing the space between them and increasing the space between them and other items on the page. This is important for showing relationships between items (e.g. showing that this button applies to this set of items) and building a hierarchy of elements on the page.
Notice the big content margin, padding and paragraph spacing on this page. All that space makes the content easy and comfortable to read.
White space also makes content more readable. A study found that good use of white space between paragraphs and in the left and right margins increases comprehension by almost 20%. Readers find it easier to focus on and process generously spaced content.
In fact the layout on a Web page (including white space, headers, indentation and figures) may not measurably influence performance but does influence user satisfaction and experience.