When you want to write special characters in a HTML document sometimes it will interpret it was code.
Here is a list of the different characters and what to replace them with..

 

left single quote ‘
right single quote ’
single low-9 quote ‚
left double quote “
right double quote ”
double low-9 quote „
single left-pointing angle quote ‹
single right-pointing angle quote ›
trademark sign ™ ™
horizontal tab 	
line feed 

space  
exclamation mark ! !
double quotation mark " "
number sign # #
dollar sign $ $
percent sign % %
ampersand & & &
apostrophe '
left parenthesis ( (
right parenthesis ) )
asterisk * *
plus sign + +
comma , ,
hyphen -
period . .
slash / ⁄ /
digits 0-9 0-
9
colon : :
semicolon &#59; ;
less-than sign &#60; &lt; <
equals sign &#61; =
greater-than sign &#62; &gt; >
question mark &#63; ?
at sign &#64; @
uppercase letters A-Z &#65;-
&#90;
left square bracket &#91; [
backslash &#92; \
right square bracket &#93; ]
caret &#94; ^
horizontal bar (underscore) &#95; _
grave accent &#96; `
lowercase letters a-z &#97;-
&#122;
left curly brace &#123; {
vertical bar &#124; |
right curly brace &#125; }
tilde &#126; ~