I have questions about categories. Is it okay to have child (nested categories)?For example:Software Development-- Web---- Java Script---- PHP---- HTML 5-- Low level---- C ---- AssemblyWhat impact will regarding SEO and search engines?In this case there three categories are just wrappers that won't contain any posts Software Development, Web and Low level.How will such structure of categories affect SEO? EDIT For example URL of post Hello World in following category hierarchy  Software Development    -- Mobile Development    ---- Android developmentWill bedomain.com/software-development/mobile-development/android-development/hello-world/For me personally it looks ugly. Development word is very redundant. But what about search engines ? 
WordPress subcategories and SEO
seo;wordpress;blog;categories
Obviously you can always have nested categories in WordPress (and most other CMSs) as well as child pages, child posts, grandchildren, etc. If done in a non-spammy fashion, there is no real advantage or disadvantage from the pure SEO perspective...the spiders don't particularly care so long as the links work and the content is indexable. The big worry is creating a spammy-looking site that appears to abuse common keywords.  As a rule of thumb I never go lower than grandchildren: Software Development    -- Mobile Development    ---- Android development <---- no lower.and try to avoid repeating the same terms in categories (e.g. development above). So a good replacement for the above could be:Development   -- Mobile   ---- Android   ---- iOSThat should handle most spam concerns.The other reason to avoid long, nested categories is simple UX. I can remember and type yoursite.com/development/mobile/android/pretty easily but yoursite.com/software-development/mobile-development/android-development/makes me tired just looking at it. So always keep humans in mind when creating nice permalinks and the SEO benefit should follow automatically. 