Yes. The Divisions between Sunnis and Shiites have persisted for the same reason that the divisions between Catholics and Orthodox Christians have persisted. Once a religious sectarian division comes into existence it is impossible to theologically heal it unless at least one side concedes that its position on the theological issues that the two sects disagree on is wrong.
However, since Catholics and Orthodox Christians have stopped killing each other and cursing each other as heretics for the last 400 years or so, it begs the question as two why Sunnis and Shiites continue to do this. (Note that the majority of Sunnis and Shiites do not feel this way, but a large vocal minority in each camp still do.) There are several reasons for this animosity.
1) Historical Grievances: The primary reason this division persists is that there has never been an atonement by either side for the pain and persecution that it has suffered when the other was in power over a given territory. Although, Shiites endured more persecution at the hands of Sunnis than the reverse, this is not to say that Sunnis have not endured persecution at Shiite hands. Both groups remain defiant that since they have the moral high-ground as granted from their faith, their actions in repressing the other sect, torturing its adherents, and murdering its leaders was progress towards removing the heresy. Compare this to the Catholics, who have apologized for the Rape of Byzantium, which was huge historical grievance between them and the Orthodox.
2) Ethnic Identities: In many countries, especially Iraq, Syria, and Lebanon, people identify "ethnically" by their sect of religion. Therefore saying somebody is Shiite in Iraq is similar to how people view being Irish-American or Japanese-American in the United States. It marks you socially and it determines who your friends are, who you marry, what jobs you take, who you love, who you despise, etc. As a result, whenever conflict has broken out, each religious group comes together to defend its people's interests. This results in political and social hatred of the other religion in addition to any theological issues.
3) Rumors of the Other's Theology: Some Sunnis think that Shiites are deluded into believing that 'Ali was a second prophet, which would violate Mohammed being the final capstone of the Prophets, a huge theological issue. Some Shiites believe that Sunnis were paid off to accept the three Rightly-Guided Caliphs before 'Ali and that Sunni Islam was therefore corrupt and ineligible to continue the Islamic tradition. Both have alleged the other was deceived by Jews, which says more about how Muslims view Jews than each other. Of course, both of these are mis-characterizations of the actual theologies of these two sects, but the point remains that as long as these problematic rumors exist, the two sides cannot reconcile.
4) Approaches to Government: Ever since the abolition of the Caliphate in 1936, Sunni Islam has been leaderless and there has come to be an understanding that religion does not participate in actual governance. (This is not a separation of church and state since the two can cooperate closely, but this prevents direct theocracy.) Shiites, on the other hand, have religious leaders called Ayatollahs who do attempt to have terrestrial authority and in Iran have actually achieved it.
the Sunnis are the majority and the shiites are the minority.therefore the numbers of Sunnis are more than shiites populations.
Answer 1Yes. However, there was no real split between Shiites and Sunnis. It is just some different views over some side issues that are not critical.Answer 2No. The split between Sunnis and Shiites occurred nearly 30 years earlier when Abu Bakr was elected by the Shoura Council to the position of Caliph against the will of Ali's supporters. Those supporters rejected the decision of the Shoura Council and became the Shiites. The Battle of Karbala crystallized this division since Ali had, by then, been assassinated, and his son Hussein (who was the next candidate supported by the Shiites) was butchered by the Caliph Yazid I without Sunnis rejecting Yazid's right to the Caliphate.
No, Shiites outnumber Sunnis in Iraq. However, Sunnis over the world outnumber Shiites. World statistics is that Sunnis Muslim world percentage is 85% of total world Muslims. While Shiites are less than 15%. Refer to question below for more information.
There is no war between them Only the extremists create problem
What caused the split was Muhammad's death in 632.
No They are not Sunnis. They are Shiites.
The Sunnis are of bigger population. Of world Muslims, 85% are Sunnis.
Some Sunnis hate some Shiites and some Shiites hate some Sunnis, but the majority of the conflicts between them are not theological, but political, social, and economic. These labels work similarly to ethnic labels in the Balkans, ripping people and countries apart. It does not help that many Sunnis and Shiites purposely or unintentionally misconstrue the doctrines of the other in order to give Divine Legitimacy to what would otherwise be a vulgar brawl for resources.
661AD
Shiites and Sunnis. However, they are not splits as for example in Chritianity different denominations. Sunnis and Shiites differe in minor Islam details. Refer to question below.
Sunnis and Shiites
Both Shiites and Sunnis are right Muslims. They differ in minor issues that are not relevant to the basic Islam rules and instructions. Refer to related question below.