How SE's follow links

[sssweb]

I have an art gallery on my site for which I devised a separate PHP navigation page that allows me to easily change the navigation sequence through the galleries, without having to update links on each gallery page. Each gallery links to the navigation page, and the nav page redirects users to the next gallery.

My question is the effect this has on SE spidering. If spiders simply read the link text on every gallery page, they will repeatedly read the link 'mysite.com/nav.php'. And since there is no gallery link list per se on nav.php (it constructs links on the fly using variable strings), there are technically no direct links anywhere on my site to each and every gallery. (I do have a Gallery List that lets you jump in at various sections, but that covers under 5% of the total gallery pages.)

Does this mean SE's can't/won't spider my gallery?

Maybe I need to set up a second Gallery List page with a complete listing.

[jonrichd]

If I understand you right, you have a link to nav.php (without any parameters) on each gallery page, and nav.php then determines the next page to go to somehow, and does a redirect to that page. If nav.php is being called with parameters (nav.php?next=101), then this advice isn't going to apply.

If this is the case, then the spider sees the contents of nav.php changing every time it follows the link. The questions I would ask include:

1. what type of redirect does nav.php do? Is it a 302 - Found redirect, a 301 - Moved Permanently redirect, or just a normal 200 OK. Any of the three of these can cause problems, depending on the engine that finds them.

2. What are you doing to determine which page to go to next within nav.php. If it's just random, that's OK, but if you're using something like the referring page to get the visitor to the next page in the sequence, remember that search spiders don't have referring pages.

This all just seems to me like a problem waiting to happen. What if you set up nav.php to to the redirect to the appropriate page, and then disallowed nav.php in robots.txt. This will prevent any duplicate content or changing content issues from happening.

Then, create some site map pages that contain static links to your various photo galleries, and make those pages accessible from the home page, and possibly the other pages on your site. You might also consider creating a Google sitemap as well, but I think you'll want the html version in any case.

When you add a new gallery page, you'll have to modify the site map page, as well as your nav.php, but that shouldn't be too hard. You'll also have the benefit of the link anchor text that describes the specific content of that gallery page, which may result in better rankings.

[sssweb]

The links to nav.php DO have parameters, but I use a simple variable with 2 options: 1 and -1. Nav.php interprets these as the 'next' and 'previous' gallery in the sequence. I then use an array of all gallery pages to navigate the sequence -- it gets the referrer page and redirects to the next or previous gallery in the sequence.

The redirect is a standard(?) PHP redirect:

header( "Location: [".$_SERVER['SERVER_NAME']."...] );

If there's no referrer (which you say applies to SE's), I redirect to the Gallery List.

Sounds like I do need to create a full gallery list with static links.

P.S. You mentioned creating a 'Google sitemap'; is this some special page that Google recommends (and which can be submitted to them) to assist their spiders, or are you simply referring to a generic sitemap that SE's (and other users) can use to link to the entire site. If it's the former, can you give a link to more info about it?