Homework / test English Social Sciences Linguistics semiotics

I have got a question that has something to do with semiotics.

The following is a paragraph taken from David Holmes' Communication Theory. I could not understand what he meant by saying collision and superimposition of signifiers?

"By allowing the construction of oppositional subjectivities hitherto excluded from the public sphere, the Internet’s inherently decentralized form is heralded as its most significant feature – allowing the collision and superimposition of signifiers and semiotic worlds in which the some sense of an authoritative meaning – a logos or a grand narrative – can no longer be sustained"

Thanks in advance