I always recommend creating copies of the original files from Microsoft. So I'm assuming that you have created a copy of the original XSL style sheet and you are going to be working on this copy.
Open your XSL Style Sheet. Before modifications, your style sheet should read as follows:
version="1.0"
exclude-result-prefixes="x d xsl msxsl cmswrt"
xmlns:x="http://www.w3.org/2001/XMLSchema"
xmlns:d="http://schemas.microsoft.com/sharepoint/dsp"
xmlns:cmswrt="http://schemas.microsoft.com/WebParts/v3/Publishing/runtime"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:msxsl="urn:schemas-microsoft-com:xslt">
<xsl:param name="ItemsHaveStreams">
version="1.0"
exclude-result-prefixes="x d xsl msxsl cmswrt"
xmlns:x="http://www.w3.org/2001/XMLSchema"
xmlns:d="http://schemas.microsoft.com/sharepoint/dsp"
xmlns:cmswrt="http://schemas.microsoft.com/WebParts/v3/Publishing/runtime"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:msxsl="urn:schemas-microsoft-com:xslt">
xmlns:msxsl="urn:schemas-microsoft-com:xslt"
xmlns:dt="urn:schemas-microsoft-com:datatypes"
xmlns:ddwrt="http://schemas.microsoft.com/WebParts/v2/DataView/runtime" >
<xsl:param name="ItemsHaveStreams">