If you ever tried adding Google Search code that will search your site to a SharePoint page using the HTML Form web part, you might get an error like this:
Unexpected System.NullReferenceException: Object reference not set to an instance of an object. at Microsoft.SharePoint.WebPartPages.WikiPageWebPartSaver.SaveWebPartsInRichText(SPWebPartManager wpmgr)
A simple way to add the Google Search for your site is to use the Page Viewer Web Part and reference an HTML file with the Google Search form code:
<!-- Search Google --> <font color="#006633" size="+1" face="Times New Roman">Search</font> <center> <FORM action=http://www.google.com/u/ursite method=GET target="_blank"> <!--mstheme--></font> <TABLE bgcolor=#FFFFFF cellspacing=0 border=0><tr valign=middle><td><!--mstheme--><font face="Times New Roman"> <A HREF=http://www.google.com/ > <IMG SRC="http://www.google.com/logos/Logo_40wht.gif" border=0 ALT=Google width="128" height="53"></A> <!--mstheme--></font></td> <td><!--mstheme--><font face="Times New Roman"> <INPUT TYPE=text name=q size=31 maxlength=255 value=""> <INPUT type=submit name=sa VALUE="Google Search" > <input type=hidden name=hq value="inurl:www.YourSite.com/subsite" > <font face=arial,sans-serif size=-1><br><input type=hidden name=sitesearch value="YourSite.com" checked> </font><br> <!--mstheme--></font></td></tr></TABLE> <!--mstheme--><font face="Times New Roman"> </FORM> </center> <!-- Search Google -->
Add the file to the sub folder under LAYOUTS: \Web Server Extensions\14\TEMPLATE\LAYOUTS\Custom\google.html
Then, add a Page Viewer Web Part (Under Media and Content) to a page and set the Web Page property to http://ServerName/_layouts/custom/google.html
Note: You may have to allow the search to open in a new window.