_content: fix some frontend label bugs

Signed-off-by: cui fliter <imcusg@gmail.com>

_content/doc/gc-guide.html

@@ -1469,7 +1469,7 @@ costs.
 
 <h2 id="Appendix">Appendix</h2>
 
-<h3 id="Additional_notes_on_GOGC">Additional notes on GOGC</h2>
+<h3 id="Additional_notes_on_GOGC">Additional notes on GOGC</h3>
 
 <p>
 The <a href="#GOGC">GOGC section</a> claimed that doubling GOGC doubles heap

_content/doc/install/source.html

@@ -440,7 +440,7 @@ To update an existing tree to the latest release, you can run:
 <pre>
 $ cd go/src
 $ git fetch
-$ git checkout <span class="versionTag"><i>&lt;tag&gt;</i></psan>
+$ git checkout <span class="versionTag"><i>&lt;tag&gt;</i></span>
 $ ./all.bash
 </pre>
 

_content/talks/2010/go_talk-20100112.html

@@ -69,7 +69,7 @@ func main() {
 	<h2>Design started in late 2007.</h2>
 	<h2>Implementation starting to work mid-2008.</h2>
 	<h2>Released as an open source project in November 2009.</h2>
-	<h2>Work continues.<h2>
+	<h2>Work continues.</h2>
 	<h2>Robert&nbsp;Griesemer, Ken&nbsp;Thompson, Rob&nbsp;Pike, Ian&nbsp;Lance&nbsp;Taylor, Russ&nbsp;Cox, many others</h2>
 </div>