MAC OS X 10.5.8 when php application error

hi again

i have using MAC OS X 10.5.8

when i run php application i got these errors

Notice: Undefined variable: row2 in /Library/WebServer/Documents/firefox/custom/expInv.php on line 99

Notice: Undefined variable: row2 in /Library/WebServer/Documents/firefox/custom/expInv.php on line 100

Notice: Undefined index: Shpt_Before in /Library/WebServer/Documents/firefox/custom/expInv.php on line 109

Notice: Undefined index: Invoice_of in /Library/WebServer/Documents/firefox/custom/expInv.php on line 112


how do i prevent those errors

plz help me with the sample code

plzzzzzzzzzzzzzz help me