what is a rag
A ‘rag’ is the uneven side of the paragraph that you are typesetting. When working with large bodies of text you are always typesetting whether you know it or not and rag is one of those concepts that once you see it, you can’t unsee it.
You want a minimal amount of whitespace on so the eyes don’t bounce back and forth on the page.
In as similar vein, you want to avoid Orphans and Widows as they produce terrible rag.
Orphans are single (or a couple) words that enter a new page at the end of a paragraph.
Widows are the last couple words in a paragraph that live on their own line.
A “rag” in typography is the uneven side of a paragraph where the text is aligned on the other side. So if the text is right-aligned, the rag is on the left side.
A good rag is one where the lines move in and out in small increments. A not-so-good rag bounces the eye back and forth from line to line creating distracting white spaces in the margin.
The easiest thing to do is to use manual line breaks where you want them. You can also change your hyphenation rules and edit your text. If those changes fail to give you the rag you want, you can then make slight adjustments in tracking, kerning, column width, page margins, or point sizes. Like many other typographic skills, the ability to do these things well requires time spent learning the techniques and time spent in practice.
A simple way to calculate the measure (best line length for font size) is to use Robert Bringhurst’s method which multiples the type size by 30. So if the type size is 10px, multiplying it by 30 gives you a measure of 300px or around 65 characters per line. Antonio Carusone
Widows are short last lines of a paragraph. A widow could be one word, the end of a hyphenated word, or two/three words left alone on the last line of a paragraph. A widow generally leaves too much white space at the end of a line, making it look like an extra blank line. The wider the line and the tighter the paragraph spacing, the more distracting the widow.
Orphans are short top lines of a page or column and are even more distracting to the reader.