Serban,
Given that this entire board is dedicated to Excel, a subject line of "Excel" doesn't give much help identifying your problem. Being more specific will help draw attention from those who might know the answer to your problem.
BTW, so far as I know, there is no way to filter by characteristics.
I think VBA is probably the only way. Examples :-
Sub Only_Hide_Bold_Cells()
Dim cell As Range
Selection.EntireRow.Hidden = False
For Each cell In Selection
If cell.Font.FontStyle = "Bold" Then cell.EntireRow.Hidden = True
Next
End Sub
Sub Show_All_Cells()
Selection.EntireRow.Hidden = False
End Sub