MACRO VBA - "run time error '1004' application - defined or object defined error"

Hi can anyone figure out why I am getting this message.. "run time error '1004' Application-defined or object-defined error"

Here is my code, the problem line seems to be:

range("A1").Select

here is the rest of the code:

Sub HorizontalLoop()
Dim lCol As Long
Sheets("output").Select

For lCol = 1 To 100
Dim inputrange As String
If Not IsEmpty(Cells(lCol).Value) Then
inputrange = Cells(1, lCol).Value
ActiveCell.EntireColumn.Select
Selection.Copy
Sheets("input").Select
range("A1").Select
ActiveSheet.Paste
Sheets("output").Select

End If

Next lCol
End Sub

Thank you in advance :)