Complex sentence: It consists of 12 guidelines (untestable) organized under four principles (websites must be "perceivable", "operable", "understandable" and "robust") and each guideline has testable success criteria (61 in all).
Split into simpler sentences: It consists of 12 guidelines (untestable) organized under four principles (websites must be "perceivable", "operable", "understandable" and "robust"). Each guideline has testable success criteria (61 in all).