So as always I have been testing a few things and looking at the methodology behind what gets classed as indexed by google and recently the focus has been firmly on looking at the impact JavScript on Google crawlers and jsut how clever have search crawlers got? All through the use of the good old img tag.
Firstly let me start with the basics of using images on a website and we will look at img tags verses css images. Where possible, img tags should ALWAYS be used, ever if it means being a bit tricky with your css (as long as its cross browser supported of course!) the core reason for this is that it gives you the opportunity to add an alt tag to the image. Now the alt tag is particularly important, an alt tag is used to tell those who browse without images enabled to determine what the image you are trying to show is and can be utilised for SEO very effectively; why is this important? well the only reason I really care about it is that Google search crawlers browse with images disabled and so can’t look at an image and say “thats a dog” you have to tell it, and that’s what the alt tag does for us.
Anyway back to the main point of the post, the intellect of search crawlers and the impact of JavaScript on index-ability.
It has been a widely held opinion for a number of years that Google crawlers are partcularly flat creatures who read html and click links and thats pretty much it.. well I can convincingly tell you, that is not the case. It seems search crawlers have become particularly advanced actually, the best name I have heard for the modern day crawler is a ‘headless browser’; they trigger javascript, the interpret html and they analyse the quality of your code and your content to make sure you have done your house keeping!
The test for this was looking at the banner on the silverchip homepage. We have some big images in here with some seo friendly (and rather unqiue) alt tags. All of the images are held in display:none; containers which is only ever changed when the JS is triggered. Now,after a quick look at Google images, I learned that all of our banner images had iin fact been indexed!
Now if this wasn’t enough another test we ran was to add a page to the website which could ONLY be accessed via a JavaScript link. We avoided visiting the image on our PC’s as to not give away its location (as I’m still a firm believe that we help Google index its pages with our day to day use of the internet) and loe un behold it was indexed…
My conclusion really from the above is that yes, crawlers are more intelligent, but a greater find is that img tags with the use of alt attributes are great ways to test search crawlers and to see exaclty what gets indexed. Google images is such a low comeptition search area that it is a great playground, throw an image up, give it a unqiue (but site relevant) alt tag and see what happens to it. Using similar alt tags to other images on the page that have genuinely been indexed and using their position as a benchmark is a good way to test and is a solid performance indicator.
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