Normally which files should be edited to add a element?

Normally which files should be edited to add a element? For example, I wanna add a "boxmail" icon in the header which links "contact us" . Thanks

In that case, you would edit tpl_header.php.

Thanks
Only tpl_header.php? nothing else files?

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Only tpl_header.php? nothing else files?

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Quote:

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I wanna add a "boxmail" icon in the header

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Yes for the header