We're a melbourne tech company in the process of building a custom site in PHP.

We plan to launch a "pre-launch" page which is also custom coded (CSS3 on twitter bootstrap framework + HTML5 front end and PHP back end).

On that site will be a link to a blog - the idea behind this is to build up ranking for a variety of relevant keywords prior to the full site going live (given the majority of the site is a member only community anyway so the blog is really the main way we'll be able to execute on-site SEO.

Ideally, we would like to install wordpress in a subdirectory on our servers and just customise the header to look the same as the landing page of the website.

But some questions and concerns...

1. Is there any detrimental effect on SEO efforts in having two separate systems (one custom PHP, the other an installation of wordpress) to manage the blog vs the rest of the site?

2. Are there any benefits or detriments to installing on a sub domain such as blog.sitename.com vs. sitename.com/blog. My preference would be sitename.com/blog as it feels neater - but open to suggestions based on knowledge of Google preferences.

3. Separately, we are building a Facebook app which is under another site name. Again because we are launching this app first, from an SEO perspective, would it actually be better to run it from a sub domain on the main site - e.g. gamename.mainsitename.com instead of on app.gamename.com? Currently we have it on app.gamename.com, but if there are SEO benefits to moving it to the other domain and server then we'll do it.

Basically we don't want to have our SEO efforts divided - will Google algorithms prefer two sites heavily referring traffic, or is it better to focus our efforts on one. I guess that's the crux of the issue. But the other one is - does Google care about traffic accessing a page built for the Facebook app iFrame - does that count toward rankings?

Sorry I hope these questions aren't too complex - but we're in the tech world every day and still can't seem to find a good answer to these ones...hence I'm taking to the forums!!

Free beer for whoever can give me a solid answer!