I needed to export some data in .Csv format from an application made totally for the browser . As usual LotusScript helped me: here are the steps I took:

• create a view with the data you want to export and call it “export”
• create an agent to be invoked by the application that physically performs the export (let’s call it exportCsv)
• in the application I insert a link in this format /folder/app.nsf/esportacsv?openagent that opens in a new window where esportacsv is the name of the agent

Then the agent:

Dim s As New NotesSession
Dim questodb As NotesDatabase
Dim vec As NotesViewEntryCollection
Dim view As NotesView
Dim nomevista As String
Dim entry As NotesViewEntry
Dim nomefile As String
Dim strn as string

nomevista = "esporta"        'view name
nomefile = "esportazione.csv"  'file name
Set questodb = s.CurrentDatabase
Set view = questodb.GetView(nomevista)  
Set vec = view.AllEntries
Set entry =  vec.GetFirstEntry

'HTTP HEADER: 
Print "Content-Disposition: attachment; filename=" & nomefile
Print "Content-Type: application/octet-stream"

strn = ""
'columns
ForAll c In view.Columns
strn =  strn &  |"| & c.Title & |",|
End ForAll

'fields
Print strn  
strn = ""
While Not (entry Is Nothing)  
ForAll  cols In entry.ColumnValues  
cols = |"| & cols & |",|
strn = strn & cols 
End ForAll  
Print strn  
strn = ""
Set entry = vec.GetNextEntry(entry)
Wend

as you can see it essentially does a series of prints but as it initially runs this

Print "Content-Disposition: attachment; filename=" & nomefile

the browser interprets it as a file to be downloaded.