I set up as below

But the problem it's replacing all lines
Even the lines that does not contain "http://www"



lcStr = FILETOSTR("header3.htm")

DIMENSION laLines[1]
ALINES(laLines, lcStr)
lcNewTextFile = "header3b.htm"
lcCrLf = CHR(13) + CHR(10)
ERASE (lcNewTextFile)
FOR i=1 TO ALEN(laLines)
if not empty(laLines[i]) && skip blank lines
IF ("http://www" $ laLines[i])
STRTOFILE(' '+ lcCrLf, lcNewTextFile, .T.)
endif
endif

ENDFOR