The Skeptic

The widespread urban legend that one swallows a high number of spiders
during sleep in one's life has no basis in reality. A sleeping person
causes all kinds of noise and vibrations by breathing, the beating heart,
snoring etc. all of which warn spiders of danger.

Visit List of common misconceptions for more.

Cognitive biases are systematic patterns of deviation from norm or
rationality in judgment, and are often studied in psychology and behavioral
economics.

Visit List of cognitive biases for more.

Article adjustment on eyewitness report. Loftus' meta-analysis on language
manipulation studies suggested the phenomenon effects taking hold on the
recall process and products of the human memory. Even the smallest
adjustment in a question, such as the article preceding the supposed
memory, could alter the responses. For example, having asked someone if
they'd seen "the" stop sign, rather than "a" stop sign, provided the
respondent with a presupposition that there was a stop sign in the scene.
This presupposition increased the number of people responding that they had
indeed seen the stop sign.

Visit False Memory for more.

The actual origin of the phrase "the whole nine yards" is a mystery, and
nearly all claimed explanations are easily proven false. Incorrect
explanations include the length of machine gun belts, the capacity of
concrete mixers (in cubic yards), various types of fabric, and many other
explanations. All are probably false, since most rely on nine yards when
evidence suggests that the phrase began as "the whole six yards". In
addition, the phrase has appeared in print as early as 1907, while many
explanations require a much later origin date.

Visit List of false etymologies of English words for more.

Misconception: The words "and" and "but" must not begin a sentence. Those
who impose this rule on themselves are following a modern English "rule"
that was not used historically. Jeremy Butterfield described this perceived
prohibition as one of "the folk commandments of English usage". The Chicago
Manual of Style says: There is a widespread belief—one with no historical
or grammatical foundation—that it is an error to begin a sentence with a
conjunction such as 'and', 'but', or 'so'. In fact, a substantial
percentage (often as many as 10 percent) of the sentences in first-rate
writing begin with conjunctions. It has been so for centuries, and even the
most conservative grammarians have followed this practice.

And you can visit Common English usage misconceptions for more.