Design & Content Guidelines
Make a well defined link architecture using few H tags the H1 Tag being used only once. The font size, text to back ground contrast all should make readability easier.The font size used should be 12 preferable or more according to the design.
Whence writing contents use a unique language not copied from any source. Include words that people type to search relevant information in the Internet.
Use low weight but high resolution images labeled and added with the correct alt text. The height and width attributes should be in the place.
Write all important information in text especially headings since the search engines cannot read text embedded in the images. Label each block of content for visitors to know what they are going to read about.
One of the important factors in on page optimization is website accessibility. This is applicable to both the users and the search engines.
The configuration of robot.txt file is important this will help keep the less desired pages from search engine crawls while informing them of important pages.
Certain scripts may not gel well with browsers and different form of machines like Ipad etc.
Check whether server is well configured. Use the DNS Check Tool:
When you conduct a ping and trace route test the load time should be less then one minute. The less load time means your website is comparatively faster than many websites.
Use the view port meta to make the site more friendly. Place reasonable distance between the links and use the font size as stated above. Above the use of flash and heavy images.
Use rich snippets to best describe your website to search engines. The structured data use should be limited and at present is restricted to products, reviews, events, local business, videos and software applications.
For better understanding read guidelines set up by search engines such as Google Guidelines