If you are looking to bolster your search engine optimisation (SEO) performance by purchasing links on useful sites, it is important to recognise the cache date of the page on which your link will be located as a valuable indicator of the page’s potential SEO benefit. The more frequently a site’s cache date is updated, the greater value it represents to your SEO efforts.
The cache date of a website is the last time that the site was visited by a search engine crawler. Upon visiting the site, the search engine automaton issues an "If-Modified-Since" request and unless the site returns a 304 (not modified) the search engine crawler downloads the contents of the page. The more frequently this cache takes place, the more beneficial to your SEO drive that the page will prove to be and the more worthwhile it will prove to purchase a link.
Many SEO practitioners believe that cache date is a greater measure of a site’s importance than Google PageRank. There are a number of reasons why this would appear to be true, considering that if you were to purchase a link one site, whilst a competitor purchased a link on a site with higher page rank, you would still reap the benefits of better SEO if your link was cached much sooner. Many in the search engine optimisation game are unsure as to whether PageRank is a very strong measure of importance at all and it is becoming more and more necessary to consider cache date in your assessment of a potential link site.
If you are considering a link exchange or link purchase with another site, be sure to check the site’s cache date before doing so. This is achieved by searching for "cache:URL" where you substitute "URL" for the actual page. The more recent the cache date the better, while a cache date of over a month is an indication that a link on that particular site might not be worth a great deal.