A participle which does not have a subject in the sentence is called a dangling participle or hanging participle.
For example, in Driving down the road, a deer leapt out in front of me, the participial phrase driving down the road is dangling: it has no subject in the sentence. Another example is given below.
- Looking out of the window, the mountains seemed very close.
Though they are not rare in speech, dangling participles are avoided in formal writing because of the possibility of misunderstanding.