When UITableView scrolled expanded cells overlap - iphone

Question

When uitableview is scrolled the expanded cells are shuffled and whole table cells are shuffled and overlapped. Why this happens and how can i set this.Please guide, thanks in advance.
Here is the code:
-(UITableViewCell *) tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell;
if(tableView == self.mTableView)
{
cell = [self.mTableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
}
if(tableView == self.mMenuTableView)
{
cell = [self.mMenuTableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
if(indexPath.section == 0)
{
if(!isShowingList)
{
cell.backgroundView = [[UIImageView alloc]initWithImage:[UIImage imageNamed:#"event_exp.png"]];
}
else
{
if(indexPath.row == 0)
{
cell.backgroundView = [[UIImageView alloc]initWithImage:[UIImage imageNamed:#"event_exp_active.png"]];
}
if(indexPath.row == 1)
{
cell.textLabel.text = [self.mArrSubMenuEvent objectAtIndex:0];
cell.backgroundColor = [UIColor colorWithRed:56.0/255.0 green:218.0/255.0 blue:250.0/255.0 alpha:1.0];
}
if(indexPath.row == 2)
{
cell.textLabel.text = [self.mArrSubMenuEvent objectAtIndex:1];
}
if(indexPath.row == 3)
{
cell.textLabel.text = [self.mArrSubMenuEvent objectAtIndex:2];
}
}
}
if(indexPath.section == 1)
{
if(!isOverhead)
{
cell.backgroundView = [[UIImageView alloc]initWithImage:[UIImage imageNamed:#"overhead_exp.png"]];
}
else
{
if(indexPath.row == 0)
{
cell.backgroundView = [[UIImageView alloc]initWithImage:[UIImage imageNamed:#"overhead_exp_active.png"]];
}
if(indexPath.row == 1)
{
cell.textLabel.text = #"Friend";
}
if(indexPath.row == 2)
{
cell.textLabel.text = #"Public";
}
}
}
if(indexPath.section == 2)
{
NSString *imgName = [self.mArrCellImages objectAtIndex:indexPath.row];
cell.backgroundView = [[UIImageView alloc]initWithImage:[UIImage imageNamed:imgName]];
}
}
cell.selectionStyle = UITableViewCellSelectionStyleNone;
return cell;
}

Answer 1

Set reuseIdentifier as nil.
cell = [self.mTableView dequeueReusableCellWithIdentifier:nil];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:nil];
}