tal:replace
This attribute will replace the entire tag with a value, or by nothing if no value is given.
<span tal:replace="string:this beautiful string">
this ugly string and span
</span>
Will produce:
this beautiful string
tal:replace can also be used to create samples in source templates, but remove them from final output.
<table><tr tal:repeat="item myresult"><td tal:content="item">item value</td></tr><tr tal:replace=""><td>sample 1</td></tr><tr tal:replace=""><td>sample 2</td></tr></table>