When I used to press the Insert in internet explorer, I was able to "type over" text. In Google Chrome it seems the Insert has no effect. How do I give it an effect (enable me to type-over text)?
You can't. A bug has been reported on Sept 26, 2011 and yet to be fixed. You can add your vote at http://code.google.com/p/chromium/issues/detail?id=98023
You can edit the text on a page by using right-clicking on the text, choosing "Inspect Element", find the text in the "Elements" page and double clicking on it. This will allow you to edit it and your changes will be reflected in the browser window. (Bear in mind that your changes are only temporary and will be long once you reload the page).