That because the table uses a reused cell that was build with the separator line, you can use two CellIdentifier one for your first row, and another for all the rest..
Try something like (didn't test the code but it should work):
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *FirstCellIdentifier = @"FirstCellIdentifier";
static NSString *OthersCellIdentifier = @"OthersCellIdentifier";
NSString *cellIndentitier = indexPath.row == 0 ? FirstCellIdentifier : OthersCellIdentifier;
CustomCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIndentitier];
if (cell == nil) {
cell = (CustomCell *)[CustomCell cellFromNibNamed:cellIndentitier];
if(indexPath.row!=0) {
UIView *lineView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, self.view.bounds.size.width, 2.5)];
lineView.backgroundColor = [[UIColor alloc] initWithPatternImage:[UIImage imageNamed:@"line.png"]];
[cell.contentView addSubview:lineView];
[lineView release];
}
}
NSDictionary *tweet;
NSDictionary *tweet= [twitterTableArray objectAtIndex:indexPath.row];
cell.twitterTextLabel.text = [tweet objectForKey:@"text"];
cell.customSubLabel.text = [NSString stringWithFormat:@"%d",indexpath.row];
}