Merge pull request twbs#15126 from Quy/master

Fix link

docs/_includes/getting-started/accessibility.html

@@ -18,7 +18,7 @@ <h3>Nested headings</h3>
   <p>Learn more at <a href="http://squizlabs.github.io/HTML_CodeSniffer/Standards/Section508/">HTML CodeSniffer</a> and <a href="http://accessibility.psu.edu/headings">Penn State's AccessAbility</a>.</p>
 
   <h3>Color contrast</h3>
-  <p>Currently, some of the default color combinations available in Bootstrap (such as the various <a href="../css/#buttons">styled button</a> classes, some of the code highlighting colors used for <a href="../css/#code-block">basic code blocks</a>, the <code>.bg-primary</code> <a href="..css/#helper-classes-backgrounds">contextual background</a> helper class, and the default link color when used on a white background) have a low contrast ratio (below the <a href="http://www.w3.org/TR/WCAG20/#visual-audio-contrast-contrast">recommended ratio of 4.5:1</a>). This can cause problems to users with low vision or who are color blind. These default colors may need to be modified to increase their contrast and legibility.</p>
+  <p>Currently, some of the default color combinations available in Bootstrap (such as the various <a href="../css/#buttons">styled button</a> classes, some of the code highlighting colors used for <a href="../css/#code-block">basic code blocks</a>, the <code>.bg-primary</code> <a href="../css/#helper-classes-backgrounds">contextual background</a> helper class, and the default link color when used on a white background) have a low contrast ratio (below the <a href="http://www.w3.org/TR/WCAG20/#visual-audio-contrast-contrast">recommended ratio of 4.5:1</a>). This can cause problems to users with low vision or who are color blind. These default colors may need to be modified to increase their contrast and legibility.</p>
 
   <h3>Additional resources</h3>
   <ul>