Any automatic citation generator will not always be accurate and may not/will not include all of the necessary information required for your citation.
If you use an automatic citation generator, check the generated citation against your chosen style's rules for accuracy.
The key to citing any source is to:
For citing material from the Web, two additional pieces of information are usually needed:
So, how do I know which style to use? How do I know the basic rules of the citation style I've selected?