The symptom you have described is very common in most people specially in myopia, that is those who have minus power. This is due to liquefying of the vitreous jelly inside the eyeball producing floaters like the one you have described. Sometimes they look like cobwebs, sometimes like dots and they float with the eye movement. They are absolutely harmless and should be ignored. More importantly if you notice any sudden flashes of light with plenty of black floaters, you should get the inside of the eye, the retina examined by an eye specialist.