Keyword proximity is nothing but the distance between the keywords.
You should place your keywords in a proper distances to get a little push in the SERP's.
Google Spiders or any search engine bots doesn't reads the content from top to bottom (not each and every pixels), That is why the word black hat SEO is still alive.
Spiders can understand the website based upon the content in it. So make the spider to easily understand your website.