How the Use of Sub-Domains Can Harm Your Search Rankings - Search Engine Watch | The MarTech Digest |
A common theme behind these issues lies in communication (or lack of it) between departments. For example, the team creating content for Old Navy's menswear section may well be completely separate from Gap's. 

This means they are creating content without any idea that they are competing with their own website, not just those of rival retailers. 

In general, only one site will rank for each term on Google, so Gap needs to decide which of the two to prioritise, or perhaps to reconsider the strategy of using sub-domains.

What is needed in each case is a co-ordinated strategy and these departments need to communicate with each other.

Individual examples may seem trivial, but if this internal conflict is happening across a broad range of keywords it can have a serious effect for businesses. 

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