Duplicate of this post on SO.
Kentico has many options to set your site up properly and have good SEO. Not knowing the internals of how your site is setup, I'd recommend digging into the following areas assuming you're using Portal Engine development:
- Settings > Content > Metadata > Page title format
- Settings > URLs and SEO > SEO - URLs
- Pages > select your main master page in the content tree > Master page in the content area > Check the second box below the title section to ensure there aren't duplicates
- Pages > select your main master page > Properties > Metadata
- Pages > select your main master page > Design tab > check for any webparts which may have some static text or head html text in them writing any meta tags.
If you're using aspx development, check your master page in code and see what there is for code in the head of your page.