Editing Template:Citation/doc (section)

===IDs must be unique===
Names, years, and hand-specified IDs must be chosen so that the IDs are unique within a page; otherwise the HTML will not conform to the W3C standards, and any references to the citations will not work reliably. For example, suppose a page contains the following two citations with {{tl|harv}}-compatible IDs:
* {{Citation |last1=Montes |first1=G. |last2=Halterman |first2=J. S. |year=2008a |journal=Pediatrics |volume=121 |issue=4 |pages=e821–e826 |title=Association of Childhood Autism Spectrum Disorders and Loss of Family Income |doi=10.1542/peds.2007-1594 |pmid=18381511 |url= http://pediatrics.aappublications.org/cgi/content/full/121/4/e821 }}
* {{Citation |last1=Montes |first1=G. |last2=Halterman |first2=J. S. |year=2008b |journal=Pediatrics |volume=122 |issue=1 |pages=e202–e208 |title=Child Care Problems and Employment Among Families with Preschool-aged Children with Autism in the United States |doi=10.1542/peds.2007-3037 |pmid=18595965 |url= http://pediatrics.aappublications.org/cgi/content/full/122/1/e202 }}

If these citations were altered to say "2008" rather than "2008a" and "2008b", the resulting page would not work, because the two different citations would both attempt to use the ID "<code>CITEREFMontesHalterman2008</code>". To avoid this problem, distinguish the citations by appending suffixes to the years, e.g. "{{para|year|2008a}}" and "{{para|year|2008b}}", as was done above. Any Harvard references to these citations should use years with the same suffixes.

It is good practice to verify that a page does not contain duplicate IDs by using the [[W3C Markup Validation Service]]; see ''[[#External links|External links]]''.