You are replacing the starting tag and then putting that back in innerHTML
, so the code will be invalid. Make all the replacements before you put the code back in the element:
var html = strMessage1.innerHTML;
html = html.replace( /aaaaaa./g,'<a href=\"http://www.google.com/');
html = html.replace( /.bbbbbb/g,'/world\">Helloworld</a>');
strMessage1.innerHTML = html;