A misplaced modifier is what some grammar books call a "dangling modifier" or a "dangling participle." Whether you intend it or not, a descriptive phrase at the beginning of a sentence modifies the very first noun that follows. Hence, if you write, "Walking down the street, a piano fell on my head," you are saying that a piano was walking down the street. I once read on a paper the sentence, "Being the early sixties democracy was not yet known in New Jersey." According to this sentence, democracy is "the early sixties." The sentence is weird enough without that misplaced modifier. I also have in my overflowing file of grammatical horrors an ad for Wendy's which reads, "As our valued guest, we guarantee to serve you" the best. In this sentence, "we" are our own "valued guest." If Wendy's wants to serve itself, it should at least make the word "guest" plural to agree with the plural "we." These mistakes abound. The sentence, "Beautiful and sensually dressed, the men noticed her immediately" could only make sense if the men were at a transvestite ball. I had to stop the car once and drive to side of the highway to write down this one from the radio: "If not caught in time, Dr. Evans said the virus will spread." Poor Dr. Evans, chased all over town. In my overflowing file cabinet of news clippings is a quote from the Christian Coalition Chief in Iowa, Bobbie Gobel, after she was fired. She denied that she had fallen from the Lord after putting her "large breast" in a parishioner’s face. She was fired, she said, for being too hard on presidential candidate Steve Forbes. In response to this charge she declared, "As a Christian, God allows me to be a fruit inspector." Perhaps if God had been a Muslim, he would have told her to keep her hands off the fruit.

This is a mistake that readers of The New Yorker and other language snobs love to snicker at. If you do not want to look ridiculous, avoid misplaced modifiers.