Hi …
Thanku for the quick reply … actually I am not getting any error… and i get data when i scroll …
my confusion is with respect to posStart and count … where r these values set? … for each scroll does it hit the server and collect the new set of data???
or is the entire data fetched into XML and from this the data is dynamically populated into grid???
i cant understand where to set the posStart 
Smart rendering can be used in two modes
a) static smart rendering - loadXML command loads all XML at once ( total_count is not specified , or equal to count of rows in XML )
b) dynamica smart rendering - loadXML loads initial XML chunk , which contains total_count value. Now, when you scroll through grid, component will check data, and if it is not loaded for scrolled part of view - additional request will be sent to server. The posStart and count values generated by script and added to the same url , which was used for loadXML operation. ( count is mimimal count of rows, which need to receive from server to render current zone of grid, can be fixed by using second parameter of enableSmartRendering command )
Technically , you can’t set posStart - this value will be set automatically if grid will need additional rows
In case of dynamic Smart Rendering posStart and count parameters are automatically passed to the server-side program which you have specified in the loadXML method.
The request (with these parameters) is sent to the server when the new portion of data is necessary.
Please, see details in the article:
dhtmlx.com/docs/products/dht … ggrid.html