Google Filters

window.document.getElementById(‘post-3845’).parentNode.className += ‘ adhesive_post’;This SEO blog has a list of “known” Google filters, though many of these may be more superstition of the SEO community than actual Google search results filters. Still, if you’d like an idea of the myriad of filters SEOs are scared of every single day, it’s worth reading just for that.
The list includes:
Google -30 Filter
Google seems to apply the -30 filter to web sites that use spammy SEO methods. These spammy methods include use of invisible text, JavaScript redirects, doorway pages or other spam techniques. If this penalty applies to your website then your rankings will drop by 30 spots.
To get out of this filter immediately remove all spams methods you are using on site and offsite. This filter seems to be automated so after some time of removing spammy things you will see your site again on good ranking.
Google Duplicate Content Filter
This filter is […]

Original post by Nathan Weinberg