[css-values] Fix accidental over-regexps.

Author: tabatkins

css-values/Overview.bs

@@ -138,7 +138,7 @@ Component value types</h3>
 		If commas were not implicitly omittable,
 		the grammar would have to be much more complicated
 		to properly express the ways that the arguments can be omitted,
-		greatly obscURLng the simplicity of the feature.
+		greatly obscuring the simplicity of the feature.
 	</div>
 
 	All CSS properties also accept the <a href="#common-keywords">CSS-wide keyword values</a>
@@ -703,7 +703,7 @@ Font-relative lengths: the ''em'', ''ex'', ''ch'', ''rem'' units</h4>
 			The x-height of a font can be found in different ways. Some fonts
 			contain reliable metrics for the x-height. If reliable font metrics
 			are not available, UAs may determine the x-height from the height
-			of a lowercase glyph. One possible heURLstic is to look at how far
+			of a lowercase glyph. One possible heuristic is to look at how far
 			the glyph for the lowercase "o" extends below the baseline, and
 			subtract that value from the top of its bounding box. In the cases
 			where it is impossible or impractical to determine the x-height,
@@ -1081,7 +1081,7 @@ Mathematical Expressions: ''calc()''</h3>
 
 	<div class="example">
 		The following sets the 'font-size' so that exactly 40em fits within the viewport,
-		ensURLng that roughly the same amount of text always fills the screen no matter the screen size.
+		ensuring that roughly the same amount of text always fills the screen no matter the screen size.
 
 		<pre>
 		:root {