Online advertising is a billion dollar industry that continues to grow due to mobile device adoption. Social Media is an increasingly contributing factor to the growth of mobile advertising expenditures. A prominent issue facing advertising scholars, marketers and publisher is source credibility in an online environment. The overall ambiguous nature of Internet based communication has left researchers, marketers and consumer with little to measure in terms of source, platform or feature credibility. Specifically, as social media modalities gain strength in strategic communication efforts, researchers will seek to uncover the affordances, features and credibility within an online environment. Message credibility can lead toward product, service or message consumption. However, with the growing number of sources, platforms and advertisers, credibility is a complex set of items to measure in an online environment. This research explores the utility of the MAIN Model for measuring technological affordances and heuristic cues available in online messaging and how it coalesces with a new breed of credibility measures. The first part of the study explores the MAIN Model for assessing technological affordances available in social media modalities. This assessment will be used to determine and qualify acts of credibility based on two dimension; expertise and trustworthiness. This is an attempt at creating a credibility scale for social media modalities and technological features and affordances. This research proposes a new conceptual framework for understanding message credibility in a social media environment for the 21st Century. The implications for identifying credibility measures in social media modalities impact both personal and commercial applications to leveraging social media platforms. This particular study has implications for marketers, publishers and advertisers leveraging modalities across facebook, twitter, instagram and tumblr.