Transforming GPS coordinates for OpenLayers

I am building a project in JavaScript that uses OpenLayers with an OpenStreetMap layer.

I have the coordinates "48.3185005, 14.2853003" (the coordinated of Linz, Austria) which I get from either navigator.geolocation.getCurrentPosition() or the Google Maps Geocoding API. Now I want to show this point on the map.

Which transformations are necessary for the map to display the correct location and how do I do these transformations with OpenLayers? At the moment, I am always getting some point east of Africa.

This is because OpenStreetMap data is a projected coordinate system, known as Web Mercator, ie, it is in meters, whereas your GPS data are in lat/lon. This is why all points appear to be in the sea off the West coast of Africa, as in a coordinate system covering the whole globe in meters, any coordinates in the range 180,180 and -90,90 will appear to be in that small area off the coast of Ghana. I notice in your original post you said East of Africa, but in a comment, you said Atlantic Ocean, from which I am assuming you meant West, which is consistent with my explanation. Is this correct?

You can deal with this in you map constructor by specifying a different map projection and display projection: see http://docs.openlayers.org/library/spherical_mercator.html

You want something along the lines of:

var map = new OpenLayers.Map("map", {
  projection: new OpenLayers.Projection("EPSG:900913"),
  displayProjection: new OpenLayers.Projection("EPSG:4326")
});

EPSG:3857 (originally 900913) is the official designation for Spherical Mercator and conversion between this and 4326 (lat/lon) is built into OpenLayers.

Would it simply be that you are mixing the values, the Point (14.2853003, 48.3185005) is in Yemen, and Point (48.3185005, 14.2853003) is in Austria..So check documentation whether the latitude & longitude values are given in different order than you think of

This should set your map in the right location.