First we need to fix all the opnsite errors like
1. Crawl Errors
2. W3c Validator
3. Is Gzip enabled
5. Save images as .jpeg and graphics as .png
6. Avoid CSS expressions
7. Reduce DNS Look ups
9. Add an Expires or a Cache-Control Header
10. Add Meta Tags(Title tags, Keywords and Description)
11. Add Alt Attribute to all the images
On page work is totally related to making a page search engine friendly.If website or web page will as much search engine friendly as much chances will get good ranking.So its very important to perform On page work very carefully and must have quality.
On Page optimization is the way of making a website SEO friendly.In On page we focus on the title tag,meta description,navigation structure,sitemap and more.If a website is well optimized then it's easy to get the ranking easily in search engines.SO on page is necessary for a website.
Write content for your site without thinking of keywords. Google will automatically assign you keywords. Your off-page links will determine your rankings. Don't fill in meta keywords fields.