capital letters for emphasis

It is better to avoid typing text all in capitals unless you are emphasizing only a few words.

The different sizes and shapes of letters are cues that we all use to recognize words. Text in capitals is harder to read because the letters are all the same height. The eyes tend to slide over a long string of words all in capitals, in search of text that is easier. Therefore, the effect is the opposite of what you want.

Also, words in capitals may seem rude, since capitals represent shouting in email and text messaging.

Other devices, such as a text box, bold font, italics or a change in font or font size, are better ways to emphasize a longer section of text.