Some of them are public and really big (they are called "Pura")and some others are just small family ones.
Buddhism, Hindu and local gods live together peacefully and the reality is that the whole of Bali smells like incense !
During our trips we have visited many of temples and here you can see some pictures.
The walls have beautifull gates and... watch out ! you are not supposed to go through all of them because some are reserved for priests :-) There are also big courtyards where ceremonies take place. But not also ceremonies.... also dance and theatre performances take place in the temples.
Flowers, palm leaves, rice, meat and plenty of fruit lying around everywhere !
It is really amazing because there is a whole industry around gifts and offerings... did you know that an average household spends at least half of its income on offerings? quite impressive... specially because many of them seem to be very poor...
Formal dresses are only required during important ceremonies but, even if you just want to explore around, don't forget to put a long cloth (sarong) around your waist and tie it tightly with a belt or sash. Some local men also cover their head.
I also read that you are not supposed to go into a temple if you have an open wound or, not sure what that is but.... also if you are menstruating you should not go there. Have to remember to ask mom about that !