Modifiers (words, phrases, clauses) which add information to your sentence are usually helpful to your readers. However, if those words or phrases are not placed correctly in the sentence, it may cause confusion or even alter the intended meaning altogether. Which is what we want to avoid!
Video Title: How misused modifiers can hurt your writing – Emma Bryce
Video Credits: http://ed.ted.com/lessons/how-misused-modifiers-can-hurt-your-writing-emma-bryce ; https://www.youtube.com/watch?v=-tX34V_XGeQ