Adverbs and adjectives are two of the trickiest elements of speech. In fact, I see them misused on a daily basis and I don’t even read all that much.
Not that misusing them will be enough to bring down your whole piece. For the most part, transgressions using adverbs and adjectives are light enough not to affect your writing too adversely.
Misusing adjectives as adverbs and vice versa happens often. That’s because it’s very easy to confuse which word a particular modifier should change. In many cases, in fact, people will be modifying a verb all while thinking they’re altering the meaning of the subject.
A few examples may be in order:
“She drives really bad.” While it looks right at first glance, it’s technically wrong since “bad” modifies the verb “drives.” As such, you should use an adverb such as “poor.”
“You should hold the iPhone horizontally when playing the game.” Again, it sounds right but is technically wrong. The modifier, in this case, should alter the “iPhone,” not the act of “holding.” As such, it should be written as “You should hold the iPhone horizontal/in a horizontal manner when playing the game.”
As we said, people get away with confusing adjectives and adverbs with each other all the time. That means your grammar checking software might end up not catching a few of these instances. The same goes for your readers, proofreaders, and editors. For the most part, they won’t really destroy the quality of your writing. Be careful when committing the mistakes during the start and ending of each block of text, however, as they tend to affect people’s overall perception rather strongly during these sections.