Fix typo.

Author: skynavga

cssom/Overview.html

@@ -1885,7 +1885,7 @@ <h3 id="css-declaration-blocks"><span class="secno">6.5 </span>CSS Declaration B
 
   <p class="note">The serialization of an empty CSS declaration block is the empty string.</p>
 
-  <p class="note">The serialization of an non-empty CSS declaration block does not include any surrounding whitespace, i.e., no whitepsace appears
+  <p class="note">The serialization of a non-empty CSS declaration block does not include any surrounding whitespace, i.e., no whitepsace appears
   before the first property name and no whitespace appears after the final semicolon delimiter that follows the last property value.</p>
 
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cssom/cssom-source

@@ -1489,7 +1489,7 @@
 
   <p class="note">The serialization of an empty CSS declaration block is the empty string.</p>
 
-  <p class="note">The serialization of an non-empty CSS declaration block does not include any surrounding whitespace, i.e., no whitepsace appears
+  <p class="note">The serialization of a non-empty CSS declaration block does not include any surrounding whitespace, i.e., no whitepsace appears
   before the first property name and no whitespace appears after the final semicolon delimiter that follows the last property value.</p>
 
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