Forum Moderators: Robert Charlton & goodroi
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Check your HTML coding at: [validator.w3.org...] and your CSS too [jigsaw.w3.org...]
This could be serious [validator.w3.org].
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Check all your internal linking using Xenu LinkSleuth or similar program.
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Make sure that non-www redirects to www for all pages of the site, and that it is a 301 redirect. Use WebBug or the Live HTTP Headers Extension for Mozilla for doing that.