Reasons for a penalty 39 | Error codes

Aside from the obvious 404 error, there are a range of others that Google really hates to see. 302 (temporarily moved) isn’t ideal; if you really must redirect something, use 301. Also, if you see any 500 errors, deal with the root cause as soon as you can. Find invisible errors with this WebConfs HTTP Header Check tool.

Reasons for a penalty 36 | Advertorials

The controversy around advertorial content was perhaps the most well known of the pre Penguin 2 debates. An advertorial is basically a page of content riddled with paid links, and often these pages were being used for aggressive manipulation of search results. The most famous example was Interflora

Reasons for a penalty 35 | Over optimization

Google doesn’t like to see too much of a good thing. An over optimization penalty usually means you’ve gone a step too far in your bid to obsessively out SEO everyone else in your industry. Cool it and publish some natural content before your rank suffers.

Reasons for a penalty 34 | Landing pages

Businesses sometimes try to use multiple landing pages in order to improve their position in SERPs. Some companies also try to improve their position by creating lots of one page websites optimized for a single keyword, then funneling users through to another site. Google considers this kind of thing to be bad practice.

Reasons for a penalty 33 | Links to suspicious sites

Never associate yourself with a website that is doing something ethically or legally dubious. Hacking, porn and malware ridden sites should be avoided. Also, try to remove links to other sites that have been penalized in the past, assuming you know about it.