Open up the previous example in Firefox. We won't be modifying any code, so any page which includes the OpenLayers library will be fine.

Open Firebug. In the console, create two projection objects:

var proj_4326 = new OpenLayers.Projection('EPSG:4326');
var proj_900913 = new OpenLayers.Projection('EPSG:900913');

Now let's create a LonLat object which will contain a point in EPSG:4326 coordinates.

var point_to_transform = new OpenLayers.LonLat(-79, 42);

And now let's transform it. We'll take it from EPSG:4326 (our source proj_4326 projection object) to EPSG:900913 (our destination proj_900913 projection object):

point_to_transform.transform(proj_4326, proj_900913);

Finally, we'll print the new value:

console.log(point_to_transform);
console.log(point_to_transform.lon, point_to_transform.lat)

Your output should read something like:

lon=-8794239...