Which of the on page elements is the most important? Please let us know all the on-page elements influencing SERPs.

Hi.
All are necessary but the most is keyword density. Keyword density must be 2-3%.

Here's on page techniques,
- Include fresh unique content
- Optimize your Title by placing target keyword in the title
- Include meta description tags, ALT tags, H1 tags
- Include well-researched keywords in appropriate density
- Place relevant anchor text
- Submit  an XML Sitemap to SE's
- Develop a dofollow internal linking structure
- Optimize your images and videos
- Reduce page loading speed

All the above listed on page factors are equally important.

Here are some on-page SEO factors to consider
    -Be hyper-relevant to a specific topic
        Include subject in title tag
        Include subject in URL
        Include subject in image alt text
        Specify subject several times throughout text content
    -Provide unique content about a given subject
    -Link back to its category page
    -Link back to its subcategory page
    -Link back to its homepage

On page optimization is back bone of any web page if you ask for any one thing then I would say that Title Tag is one of the best things of on page optimization that can't be neglect for search engine optimization. There is a link that can help you to optimize title tag better then you have done never before
http://www.seomoz.org/learn-seo/title-tag

Keyword optimization, content optimization, Meta data information such as title, description, keyword, internal linking, image optimization, URL optimization, Heading tag and etc. are these very important in the on page optimization.

All are important elements, but do take care of keywords, because from the keywords your site will be visible in search engine. So always choose best keywords for your site with good density. ALT tags, internal linking, make your content unique. These all factors are important role in on page.

There are several important things in onpage optimization. Every page should contain unique title and description. Use header tags to highlight important sections of webpage. fill alt tags with relevant keywords, internal linking structure, highlight important key phrases in the content.

According to me Metatags, ALT tags, sitemaps and robot.txt are some of the important on-page SEO tools.

As per my knowledge meta data and content are most powerful element in on page SEO. Because unique and relevant meta tags are helps in ranking, traffic where informative and quality content decrease your website bounce rate.

HI
selection of keyowrds and conetent is the important things, good keywords quality content can help is achieving high rank fast. 

Great content, good keywords and a good social media campaign.
http://www.zeuscreative.co.uk/creative-web-design
http://forums.thinkbroadband.com/webdesign/f/4093641-how-to-get-a-wwwmysitecom.html#Post4093641

i would say URL and Title of the page is most important

Page content and meta,s (title and description) are the main factors of onpage. Never ignore these factor in onpage.

My point of view "keyword" is most important on page element.

 
The Title Tag is the first and most important on-page element for achieving good page rank. Check that the main website search term is included in this tag, and place it as near to the front as is reasonable, whilst ensuring that it reads well.

Join forums and message boards related to niche. If it is permitted, link to your site or blog when/where you can. Other people on the forum are very likely to check out your site.

We know that content is always king.
So content is the main on page element.

On-page optimization is a basic and important process in promotion of your website because it is use for make your website as search engines criteria or make your website SEO friendly using on-page optimization techniques. In which you use some changes in your website's source code but these changes don't show in front of your  website and they run in background of your website. It is use for inform to search engines about your website theme so that when users search in search engines related to your website, search engines can show your website. You should use following techniques for make your website SEO friendly

* Select right keywords
* Add Meta(Keywords, Description..)
* Use your targeted keywords in Title
* Use unique and relevant keywords in each page of your website
* Image optimization
* Title optimization
* Use H1/H2..
* Use unique content
* Try to Avoid flash, Java scripts, frames

according to me all elements are necessary in onpage such as site url, structure, title, meta tags, sitemap, content etc.

When it all comes down to it there are a lot of important factors to on-page optimization. You want to make sure to select good keywords, use them in your title, and try to use them on all of your pages (just be careful not to go too crazy with them. Another big thing is to make sure to use unique content, you want your site to stick out from the rest.

All on page element is helpful. There is no most important. All should be done accordingly to get higher result.

There are various element that are necessary for a page like in on page seo:-
1.title
2.keywords
3.description
The most important keyword density.

Fresh, unique content is the most important aspect of on-page seo. But, also important is maintaining the quality of the coding, internal links, optimization of the title, a good ratio of keywords in the actual content, meta tags, etc.

Meta tags, meta description, proper internal linking, keyword density, H tags and alt tags are most important in on page seo 

The most important facts in on page are title tags, H tags, Meta keywords and description, alt tags,anchor tags, content, internal linking.

URL optimization
Heading tag
title
description
keyword
Keyword optimization
content optimization
Meta tags
internal linking
image optimization

these very important in the on page optimization.

Title Tags, H tags, alt tags meta items,content, navigation structure are Internal linking are some basic and most important job of on page seo.

All On page activities are important. Most important content should be unique or fresh and use relevant keywords.

Image optimization
Keyword optimization
Meta tags
Header tags
URL Naming
Heading tag
Meta title
Meta description
All of these steps are important part of on page SEO.