A very common and innocent mistake can have worst consequences. It generally happens when a webmaster on the Client's side is updating a Web site, perhaps simply adding a press release or uploading a graphics or re-wamping / re-skinning a website by removing many of the elements that the search engine optimization professional had added to achieve high rankings. This can result in a loss of positions for which the SEO is responsible.
Worst thing is that, since most sites are developed on a testing basis, damage can be done when the site goes live. Testing is not intended to be crawled by search engine spiders, and so responsible webmasters include instructions in the website code Robots.txt with message "Disallow". The major search engines regularly follow this robots.txt file from its server to crawl and Index website pages. The Search Engines also crawl the pages when the changes are made at the Client's side without this file making those pages index by the search engines that is not intended by the SEO. Such a mis-communication is somewhat less than ideal. Once again, the SEO generally is responsible.
Since constantly accepting blame can be discouraging and a good SEO observes the code on all the webpages of the site on a daily basis, analyzes any changes, and quickly reacts if anything potentially harmful has been done. In this way the Web site can be repaired before ranking losses occur. But it is left to the fate of the client to perform worstly when there is a mis-communication between the SEO and the Client side webmasters.
