Another reason against copy-pasting from the web is using unicode characters that look like ASCII ones. This was on HN a week or so ago, but it doesn&#x27;t hurt to repeat.<p>Example shell command:<p><pre><code>    eⅽho &#x27;hello world&#x27;
</code></pre>
Copy-pasting the above command will fail with the message `eⅽho: command not found`. The reason? &#x27;ⅽ&#x27; in &#x27;eⅽho&#x27; is a unicode character &quot;SMALL ROMAN NUMERAL ONE HUNDRED&quot; that looks <i>identical</i> to regular ascii &#x27;c&#x27;.<p>The above can also be mis-used for any programming language, not just shell commands.