I would also agree with MamaBear61 that cutting the strips the WOF is a safe assumption. Take a look at your pattern again, it may state something like 'unless otherwise specified cut strips WOF'. WOF means from selvedge to selvedge, or if you are using fat quarters, cut perpendicular to the selvedge. YouTube has a lot of videos on fabric cutting for beginning quilters. Here's one:
http://www.youtube.com/watch?v=LjQNY9j_PIQ
I went and looked at the picture of your quilt and it's titled "Purple Haze: Easy Scrap Quilt". For a scrap quilt, you use scraps of whatever you have, which may or may not be a full piece of fabric so the length is not specified. Cut strips WOF, then sub cut until you get the number of pieces required for your quilt.