Wherever you heard it, please do yourself a favor and stop reading biased propagandic websites which spread lies. You'd be so much better off without them.
The Israeli flag is compromised of 2 Jewish symbols. Magen David, also known as "The star of David", One of Israel's most famous kings in the bible, the one who fought against Golliath. The 2 lines represented the "Tallit", a prayer shawd used by Jews. Here's a picture:
http://www.kodeshop.com/images/tallithtsemer.jpg