Blue Chips Edge Down, Apple Lifts Tech  NEW YORK (Reuters) - Blue-chip stocks fell slightly on  Monday after No. 1 retailer Wal-Mart Stores Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=WMT.N target=/stocks/quickinfo/fullquote"&gt;WMT.N&lt;/A&gt;  reported lower-than-expected Thanksgiving sales, while  technology shares were lifted by a rally in Apple Computer Inc.  &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=AAPL.O target=/stocks/quickinfo/fullquote"&gt;AAPL.O&lt;/A&gt;.