Some portion of the report is not coming after printing it

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ASP.NET

Javascript

I am working in a report a page. A JavaScript function is used to print to page. But in the printed version of the report some portion of the report is not coming. What may be the probable reason of this issue??
Here is the JavaScript function:

function doprint()
			{
				document.all('btnPrint').style.visibility =  'hidden';
				document.all('btnClose').style.visibility =  'hidden';
				try
				{
					if (factory == null)
					{
					     window.print();
					}
					else
					{
						if (factory.printing == null)
						{
						    window.print();
						}
						else
						{
							var h = factory.printing.header;
							var f = factory.printing.footer;
							//set header and footer to blank
							factory.printing.header = "";
							factory.printing.footer = "";
							//print page without prompt
							factory.DoPrint(false);
							//restore user's info
							factory.printing.header = h;
							factory.printing.footer = f;
						}
					}  
				}
				catch(e)
				{
					window.print();
				}
       
				//show the print and close button
				document.all("btnPrint").style.visibility = 'visible';
				document.all("btnClose").style.visibility = 'visible';
			}

Thanks in advance