Before the premiere of The Walking Dead, AMC laid out some official rules for how their brand of zombie would behave. Given their revolving door of showrunners working in what could easily become a pretty repetitive environment, it's pretty predictable that several of these rules were eventually violated.
There have been numerous examples pointed out by die-hard Walking Dead fans, but one of the most glaring is "Zombies have poor eyesight, but they do have a strong sense of smell." Given this rule, it seemed ridiculous that in season one's "Guts," Rick and Glenn could just slather themselves with zombie intestines to avoid being smelled out by walkers. In the season two premiere, the gang ducks underneath cars without rubbing themselves in zombie parts, and they still avoid detection. It's a safe bet that the minds behind the highly rated show aren't too worried about these inconsistencies.