ExpertRec　is　a　collaborative　Web　search　engine,　which　is　differ　from　current　main　search　engine　and　allows　users　share　search　histories　through　a　Web　browser　toolbar　or　a　proxy　browser.　In　addition,　it　can　be　taken　as　a　novel　social　Web　search　engine　and　utilize　expert＇s　search　histories　for　building　recommendations.　In　this　paper,　we　give　an　anatomy　of　ExpertRec　and　specially　introduce　its　architecture　and　core　techniques.　It　includes　two　basic　components:　a　client　agent　and　a　back-end　server.　The　former　is　implemented　as　a　Mozilla　Firefox　toolbar　(a　Firefox　extension),　which　can　integrate　with　mainstream　search　engines　like　Google,　Yahoo!,　et　al.,　to　meet　users＇　teamwork　needs.　And　it　allows　users　to　generate　high-quality　tags,　votes,　comments　over　current　Web　including　search　histories,　personal　archival　content　in　local　host　typically　beyond　the　reach　of　existing　Web　2.0　social　tagging　system.　The　latter　is　a　CBR　(case-based　reasoning)-based　recommendation　engine　and　implemented　according　to　some　core　techniques,　such　recommendation　rules,　a　scalable　method　to　identify　search　expertise　based　on　a　hierarchical　user　profile　in　order　to　improve　users＇　search　quality,　and　so　on.　Finally,　we　give　an　evaluation　and　make　conclusions.　©　2011　Springer-Verlag.