These are modifiers that are not clearly identified with the words they modify. The closer a modifier is to the word it modifies, the clearer a sentence will be.

EXAMPLES:
I sitting on the couch, watching television. (INCORRECT)
Sitting on the couch, I watch television. (CORRECT)
Having seen the movie once, there is no reason to see it again. (INCORRECT)
Having seen the movie once, I have no reason to see it again. (CORRECT)
Looking at the neighbour, the telephone rang. (INCORRECT – it appears the telephone was looking at the neighbour.)
I was looking at the neighbour when the telephone rang. (CORRECT)