Structural analysis of web pages has been proposed several times and for a number of reasons and purposes, such as the re-flowing of standard web pages to fit a smaller PDA screen. elISA is a rule-based system for the analysis of regularities and structures within web pages that is used for a fairly different task, the determination of editable text blocks within standard web pages, as needed by the IsaWiki collaborative editing environment. The elISA analysis engine is implemented as a XSLT meta-stylesheet that applied to a rule set generates an XSLT stylesheet that, in turn, applied to the original HTML document generates the requested analysis.