From the Hamilton College Writing Center's Seven Deadly Sins of Bad Writing: http://www.hamilton.edu/writing/sins.html
The Fifth Deadly Sin: Misplaced and Dangling Modifiers
Misplaced and dangling modifiers create illogical, even comical, sentences. We confuse our readers if we fail to connect modifiers (words that describe or limit other words) to the words they modify; be sure to place modifiers next to the words they modify. See the illogic in this example:
Walking back from the village, my wallet was lost. (Does your wallet walk?)
revised: Walking back from the village, I lost my wallet. (Your wallet doesn't walk, but you do.)
A misplaced modifier is a word or phrase that due to its placement mistakenly refers to the wrong word. The modifier truly is misplaced.
To correct a misplaced modifier, move it next to or near the word it modifies.
A fine athlete and student, the coach honored the captain of the tennis team. (The coach was not the fine athlete and student.)
revised: The coach honored the tennis team's captain, a fine athlete and student.
Limiting modifiers (only, almost, nearly, just) are commonly misplaced. To avoid ambiguity, place them in front of the word they modify.
Marsh's evidence reinforces the view that the artist only intended the images for a local audience.
revised: Marsh's evidence reinforces the view that the artist intended the images only for a local audience.
A dangling modifier is a (usually introductory) word or phrase that the writer intends to use as a modifier of a following word, but the following word is missing. The result is an illogical statement.
To fix a dangling modifier, add the missing word and place the modifier next to it.
Acting on numerous complaints from students, a fox was found near Root. (The fox did not act on the complaint.)
revised: Acting on numerous complaints from students, security found a fox near Root.
After reading the original study, the flaws in Lee's argument are obvious.
revised: Reading the original study reveals obvious flaws in Lee's argument.
Dangling modifiers go hand-in-hand with wordiness and passive voice.
Correct one and you correct them all!