Google Has Not Visited the Site to Index it Yet
This is likely the most common reason. Google doesn't know about the new site, so it wont have added it to the index. Google discovers new websites by several means…- Using a website submission form at https://www.google.com/webmasters/tools/submit-url?continue=/addurl&pli=1. Generally your web developers should do this.
- Using a website site map XML file that is submitted to Google Webmaster Tools. Google provides web developers a very useful tool for managing websites with Google, and the tool allows developers to submit a website and all its pages to Google, to inform Google what pages exist on a website. Your web developers should do this too.
- By indexing other websites that have added a link back to your website, and then following that link to discover your new site.
Google Has Indexed It But Keywords You Are Using Do Not Show Results
It may be that Google has actually indexed your site but certain keywords you are using will not show results. Searching for your site directly as above will inform you if its indexed or not. If it IS indexed, then your website may not be optimised for the keywords you are using to search for it. Several factors exist in order to rank high for the keywords you are using to search for it:-- The keywords, and more importantly the phrase, you are using needs to be within the content on the website. Ideally it should be a page title, a page heading and then within the content. This may help the site rank higher for these keywords.
- Having the keywords or phrase as anchor text in backlinks from other websites to your site will help Google associate your site with that phrase. e.g. linking the phrase "Web Design Caerphilly" to www.amityweb.co.uk on another website, will help Google make the connection between keywords and the website. Note: there are other factors to take into account, especially since the Google Penguin update, which is beyond the scope of this blog post, nevertheless it's still relevant!
- Competition. If you have optimised your site for the keywords as in point 1 yet still are not ranking high, then competition could be a key reason for this. Competition, e.g. other websites that are optimised for the same keywords and phrase, is one of the main reasons for not ranking high, and one of the most difficult to tackle. For example, if you are the only provider of "web design in caerphilly" then it is likely your site will rank high for this phrase one that phrase is added to the site. But if you are one of say 20 providers of web design in caerphilly, and considering Google by default shows 10 results on a page, and then consider that the other 19 companies are all trying very hard, and maybe even spending a lot of money, to search engine optimise their websites for this phrase, then it is likely your site will not rank high with little optimisation effort. You would need to invest more time and effort into search engine optimisation to compete with the others doing it.