What is the role of acid in keto enol tautomerism I have heard about an acid acting as a catalyst in keto enol tatutomerism.I have yet to understand the mechanism of the reaction though.pictorial depictions are welcome.
In acid-catalysed keto-enol tautomerism, a lone pair of electrons is removed from the oxygen of carbonyl group by the acid.
 

If enol is the starting compound, markovnikov's addition of $\ce{H+}$ occurs.