Here at WPW there is written much about SEO, but the subject in the heading has not been treated in a systematic manner as far as I know. I found and interesting article about this subject at Sitepoint. Here is the conclusion for the big three:
"Thus, this experiment established the fact that the leading search engines differ considerably in terms of the the amount of page text they're able to crawl. For Yahoo!, the limit is 210KB; for Google, 520KB; and for MSN, it's 1030KB. Pages smaller than these sizes are indexed fully, while any text that extends beyond those limits will not be indexed".
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