coburn - 6:39 pm on Aug 18, 2004 (gmt 0)

Walkman, your question is too generalised to give an exact answer to.

I've found that for competitive phrases, new backlinks can take 6 weeks to affect the SERPs. I'm guessing your backlinks use your chosen anchor text. So have you kept track of your backlinks? Perhaps you were linked to by an authority site, and they have since dropped you from their listing? So many factors we can only conjecture without more facts.

PatrickDeese makes an important point about your competition not standing still (don't assume 'Ceteris Paribus' - go out and actively model your competition to 'borrow' their secrets! I think someone once called it 'research').

Rather than re-arrange your 'deck chairs on the Tatanic' (onpage), work on sailing more effectively (offpage bl's using anchor text).