How can I match on an attribute that contains a certain string?

Question

I am having a problem selecting nodes by attribute when the attributes contains more than one word. For example:

Answer 1

EDIT: see bobince's solution which uses contains rather than start-with, along with a trick to ensure the comparison is done at the level of a complete token (lest the 'atag' pattern be found as part of another 'tag').

"atag btag" is an odd value for the class attribute, but never the less, try:

//*[starts-with(@class,"atag")]