A selection in a browser in an integrated development environment can be mapped back to the original document that was fetched from a web server by uniquely identifying elements in the original document. A DOM can be created from the original document where the DOM retains the unique identifiers associated with the elements. Block lists for the original document and the DOM can be created. A differencing algorithm can be run on the two block lists. A selection in a browser can be mapped to a location in the DOM block list and the location in the DOM block list can be mapped to the original document.