What JSR version Liferay implements? Why JSR compatibility is important while choosing a portal?

JSR is a "Java Specification Request". Liferay Portal is developed to adhere to JSR 168 and JSR 286 specifications.  
This specification is created by committee of JEE portal vendors. This specification is designed to achieve interoperability between different portals and portlets.  
Liferay supports mainly below JSRs. 

• JSR-168(Portlet 1.0)  
• JSR-286(Portlet 2.0)  
• JSR-127(JSF 1.0)  
• JSR-170  
• JSR-314(JSF 2.0)  
• JSR-329