From Seo Wiki - Search Engine Optimization and Programming Languages
"Click here" is a verb phrase that may be used as the anchor text of a hyperlink on a web page. The World Wide Web Consortium, through its Quality Tips for Webmasters, advises web designers to avoid using "click here" for this purpose.
Jakob Nielsen, a leading web usability pundit, says, "Don't use 'click here' or other non-descriptive link text."  According to web programmer Jutta Degener, "If you owned a shop, you'd write 'Welcome' on the door, not 'Open this door to enter the shop.'"
Search engines use anchor text to index the content of a linked-to site. For example, a site that is linked with the same anchor text phrase by many other sites may appear towards the top of searches for that phrase. Some bloggers have speculated that using "click here" in lieu of a descriptive name is a poor search engine optimization practice. 
Accessibility and device dependence
Screen readers, used by the visually impaired, can read out only the hyperlinks on the page as a quick method of navigation. Usability and accessibility firm Webcredible advises avoiding non-descriptive link text such as "click here" at all costs, as it makes no sense whatsoever out of context. 
In addition, mobile phones and other devices without a mouse similarly have no clicking when a link is selected with the keypad. With increasing numbers of touchscreen devices, a related phrase now emerging is "tap here".
Users may want to print web pages for reference. "Click here" is inapplicable on the printed page. For this reason, Tim Berners-Lee, the inventor of the Web, advises web designers to try to avoid references in the text to online aspects. 
- ↑ World Wide Web Consortium QA Tips, contributed September 2001 by Aaron Swartz
- ↑ Jakob Nielsen's AlertBox: October 3, 2005: Top Ten Web Design Mistakes of 2005
- ↑ What is good hypertext writing?, Appendix: Dangerous Words, Jutta Degener July 1998
- ↑ Solo Signal, "SEO Tip: Please Don’t Click Here"
- ↑ Frances Thorsten, Realty Blogging, "SEO Tip of the Day – No More 'Click Here' !!!"
- ↑ Improving usability for screen reader users, OUT-LAW News, July 21, 2005
- ↑ Style Guide for online hypertext, Tim Berners-Lee 1992-1998.