Information and communication technology trigger a plethora of linguistic issues regarding the nature of the emerging, mercurial medium of computer-mediated discourse (CMD). Using some selective linguistic features outlined in Biber's Multi-Dimensional, Multi-Feature model (1988, 1995 and 2004), this study conducts a computer-mediated discourse analysis (CMDA), namely a microlinguistic analysis, of two computer-mediated communication (CMC) modes: web chat, a principal manifestation of synchronous CMC, and text messages, a principal manifestation of asynchronous CMC, from the perspectives of lexis, grammar and phonology. Findings showed that despite the different conditions of language production, including time, space and situations, of web chat and text messages, they share many linguistic features, with different frequencies, at the lexical, grammatical and phonological levels. Much of the differences between both modes are ascribed to users' creativity, technological facilities, and communication situation.