This should work fine (using .text():

$("#toptitle").text("New word");

Something like this should do the trick:

$(document).ready(function() {
    $('#toptitle').text(function(i, oldText) {
        return oldText === 'Profil' ? 'New word' : oldText;
    });
});

This only replaces the content when it is Profil. See text in the jQuery API.

Something like this should work

var text = $('#toptitle').text();
if (text == 'Profil'){
    $('#toptitle').text('New Word');
}

Could do it with :contains() selector as well:

$('#toptitle:contains("Profil")').text("New word");

example: http://jsfiddle.net/niklasvh/xPRzr/

Cleanest

Try this for a clean approach.

var $toptitle = $('#toptitle');

if ( $toptitle.text() == 'Profile' ) // No {} brackets necessary if it's just one line.  
  $toptitle.text('New Word');         

$('#toptitle').html('New world');

or

$('#toptitle').text('New world');

Pretty straight forward to do:

$(function() {
  $('#toptitle').html('New word');
});

The html function accepts html as well, but its straight forward for replacing text.

*In my case i have stored the new Value in the var altText

$('#toptitle').text(altText);

*
And it Worked