If your keyword doesn't seem relevant or doesn't perform well over time, I would suggest that you delete it. When you delete it, try creating another keyword which provides more useful information about your products or services. Don't delete an inactive keyword and then add it back to your account at a later time. The Adwords system will remember its performance history, even if you re-add it to a different ad group.
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[edited by: engine at 10:51 am (utc) on Feb. 25, 2008]
[edit reason] No sigs, thanks, See ToS [/edit]
I just can't increase the quality score because the rule is not clear. In fact, those ad copy and keywords is come from Google optimization team. It seem that google people it self do not understand how to optimize for adwords.
They offered me the optimization after I ask why I get poor quality score with relevant keywords, relevant ad copy, and relevant landing pages/site.
And after running their solution for several days, I got poor quality score too. So I think quality score is just their way to get more from their money.
So, back to my question, if I let inactive keywords in my campaign and don't do anything to fix those keywords, will it change it's status to active in the future?
From Google:
"Quality Score for minimum bid is determined by a keyword's clickthrough rate (CTR) on Google, the relevance of the keyword to its ad group, your landing page quality, your account's historical performance, and other relevance factors."
If the keyword is extremely important to your business then I would optimise my landing pages to match the keyword and then start a new adwords account with different details so that I didn't have to fight against a poor history.