A question related to UIButton

Question

Hi,

I have put UIButoon dynamically by code It is like this,

    first_name_textfield = [[UITextField alloc] initWithFrame:CGRectMake(123, 5, 175, 31)];
first_name_textfield.delegate = self;
first_name_textfield.borderStyle=UITextBorderStyleRoundedRect;
first_name_textfield.textAlignment = UITextAlignmentLeft;
first_name_textfield.autocorrectionType = UITextAutocorrectionTypeNo;   
first_name_textfield.autoresizingMask=[];
first_name_textfield.keyboardType = UIKeyboardTypeDefault;  
first_name_textfield.returnKeyType = UIReturnKeyDone;
    first_name_textfield.autoresizingMask =UIViewAutoresizingFlexibleWidth;
//first_name_textfield.clearButtonMode = UITextFieldViewModeWhileEditing;   
[self.view addSubview: first_name_textfield];
[first_name_textfield release];

but when i click on UIButton my cursor is not touch from top to bottom to the UITextField but it touches top and not upto bottom slightly then this why is it so?