It is recommended that you limit  your document  libraries to no more than
2000 items per folder for best performance.

See these guidelines:

WSS 2.0 - Capacity Planning for Windows SharePoint Services 2.0
(About Capacity and Scale Guidelines) -
technet2.microsoft.com/.../6dc31165-
1fe2-4353-9c49-a87aef5ed6091033.mspx?mfr=true

WSS 3.0 - Plan for Software Boundaries:
technet2.microsoft.com/.../b69cf608-
fa92-4143-a2c4-0a40659b2e6e1033.mspx?mfr=true

Office SharePoint Server 2007 - Guidelines for Acceptable
Performance: http://technet.microsoft.com/en-
us/library/cc262787.aspx#section3

but I am using the wss  2.0, Sharepoint 2003 any article/whitepaper available
on this ?
and also by wss object model uploading  file calculate the lenght of file,as
it is int type
so what happen for large type of file? necaue int has limitation
can we change to another type?

Yes. your performance starts dipping at ~500 items and really starts to
tank at 2000 items. You can mitigate this reduction in performance by
using 1. Views filtered by an indexed column 2. Folders 3. User
education.

Note that folders are twice as efficient as indexed views. You can see
some of this here
office.microsoft.com/.../HA101736671033.as
px?pid=CH101215281033 and a whitepaper here
go.microsoft.com/fwlink/?LinkId=95450&clcid=0x409 (URLS may
break, so paste them together)

You can see the visuals of a Visual Studio 2005 stress test here:
technet.microsoft.com/en-us/library/cc262787.aspx

And more general ECM info here:
technet.microsoft.com/en-us/library/cc263028.aspx

Is this applicatible to the Sharepoint 2003 and wss  2.0 Document library  ?

Using folders to limit  items in a view - yes. indexed columns - no.

Be aware, folders in 2003 were only available in document  libraries, not
lists.

SharePoint v2 and v3 both have "the rule of 2000". While you can put
more items into any container, when you go beyond 2000 the performance
curve degrades precipitously. In WSS v3 they've given us Folders as
containers in all lists/libraries and indexed columns to help mitigate
this degradation but you must design your solution with this in mind.

Some rudimentary ideas here:
office.microsoft.com/.../HA101736671033.as
px

This blog post and white paper on large list support go much deeper:
blogs.msdn.com/.../scaling-large-lists.
aspx
go.microsoft.com/fwlink/?LinkId=95450&clcid=0x409