DOE is an acronym that stands for Depending on Experience, and it is an indication that an open job position's salary is based on the amount of experience the job candidate has. The more work experience someone has in a particular field, the higher the salary generally is.
Entry-level professionals generally are offered a salary at the low end of a job's salary range, because these people typically have little work experience in their field. Some advertised jobs may list the wages as competitive, and some may list the wages as DOE. A candidate may prefer to know what his wages may be, but some general research into the field can help a candidate determine his overall market value for the open position.