How many times does a keyword need to appear in content?

Befor looking 4 answer of keyword density, one must understand what are keywords.
These are the key words of your content. And imo their density is strictly content related. You have not to make any extra effort, just write your content lucidly.

 

5% is enough. More than that would create a dull impression,
go as much, as you can afford

 

i will answer what the thread starter asked:
using and limitation of keyword depends on where you are using.
1. don't use keywords more than 2 times in page title
2. As per google instructions, whatever keywords you are putting in meta tag keyword--should be compulosry used in the content of ur site. If you won't use your page will be penalize...its fact. you can use at the most 63 keywords in meta tag..however it depends on how big is your page content..if page content is small restrict your keywords to 5-10 in meta tag
3. h1 and h2 tag should start with ur keyword, use only one keyword and description should not be more than 10 words.
4. don't dump keywords unecessarily in page contect. studies shown that density of your keyword in page content should be between 2-4 % only.
If any further query mail me at or pm me.