Red and Yellow Lines

[Uzoma]

I would be very grateful if someone would please explain which lines are not safe for parking on and when they are/are not?

[JohnThorn]

According to the Highway Code, a single yellow line means no parking during the working day. A double yellow line means no parking for more than the working day (usually never), a dashed yellow line means no parking for less than the working day (often a one-hour or two-hour limit) There will always be signs nearby. Yellow lines on the kerb at right angles to the road are restrictions on loading and unloading of goods.
Even with a yellow line, you may stop to let a passenger in or out, or to take on fuel or water. But red lines mean no stopping AT ALL. Again, look for the signs nearby.