http://help.arcgis.com/en/webapi/javascript/arcgis/help/jsapi_start.htmmap.setLevel(level) Sets the map to the specified level ID. Zooms to the new level based on the current map center point. Valid only with an ArcGISTiledMapService layer.
Or for example:map.setExtent(esri.geometry.getExtentForScale(map, scale), fit?)
Second: Don't mess the JS-API with the dojo library. Dojo 1.6.1 is shipped with the JS-API. You refer to:<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/dojo/1.6/dojo/dojo.xd.js" djConfig="parseOnLoad: true"></script>
and <script type="text/javascript" src="http://serverapi.arcgisonline.com/jsapi/arcgis/?v=2.4"></script>
and your CSS is coming from:<link rel="stylesheet" type="text/css" href="http://ajax.googleapis.com/ajax/libs/dojo/1.6/dijit/themes/claro/claro.css"/>
You only need:<link rel="stylesheet" type="text/css" href="http://serverapi.arcgisonline.com/jsapi/arcgis/2.4/js/dojo/dijit/themes/claro/claro.css">
and <script type="text/javascript" src="http://serverapi.arcgisonline.com/jsapi/arcgis/?v=2.4"></script>
It's possible to use another DOJO version with the JS-API but I guess you don't need that yet. I advice you to read the Concepts at: http://help.arcgis.com/en/webapi/javascript/arcgis/help/jshelp_start.htm and check the basic examples in the documentation.Hope that helpsAxel