What are open source tools for building a web gis application having PAN, Zoom, Query/search, Label etc options?

I have decided to use PostgreSQL for database and GeoServer as middleware but I am a bit confused in selecting the software to design the GUI for the client side.

I am a novice programmer, so will geoexplorer be a good option or are there some other tools which can be more easily customized for my work?

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