In gel electrophoresis, if different band size and no. of bands, why different? If not, why is it so?. *** help me...

How is SYBR Safe DNA gel stain better than the conventional ethidium bromide staining method? Who can tel me?. thanks..

I'm not sure what you are asking but...
Number of bands is the number of DNA fragments you have on your gel. For example, if there are two bands, there are two DNA fragments there.

Band size reflects the length (# of nucleotides) of that particular DNA fragment. The larger the band, the longer that DNA fragment is.