SEO Caveats

Beware of guarantees. I don't offer one myself. I can optimise and optimise and then the following week or month the engine may change its algorithm (the criterion by which it ranks each site) and the site may tumble in the rankings. This is not so bad as it sounds as it's the same for everyone.

It should be noted that neither I nor anyone else have control over the independent actions of either the engines or of other web designers. I won't guarantee a first place in any engine. How can I? Answer is I can't and neither can anyone else so I'd avoid any company that says it can. I also won't guarantee a top ten placing in any engine. How can I? What's to stop any other ten designers at any time from producing sites out of the blue that are well-optimised and contain a great deal more relevant content? Answer? Nothing. In practice of course this is extremely unlikely to happen but since I cannot absolutely determine that it won't I'd be unwise and dishonest to guarantee otherwise.

In general though if your site has never been optimised and has a lot of superfluous code in it (many do) then in all probability careful optimisation will result in improved rankings. Exactly how much will depend on both the amount and the quality of the opposition.
But don't get taken in by false promises. Remember, there are always SEO Caveats.