let's say we have the keyword widgets
I would go do a search on widgets and only see 3 adword ads, and not one of them would be my company. Now if we were the low bidder, why doesn't it just put us at the bottom? We have a fairly good sized budget cap set on the keywords, and according to our statistics, we have rarely hit the max.
So what's the deal with Adwords? Whatever is happening has happened in the last few weeks because our visitor count and sales lead count have both taken a header in that time.
1) You are approaching your daily budget for that keyword. If there are a few hours of the day to go any you are approaching your daily budget, Adwords will not show your ad every time. If this is the problem, simply increase your budget for that keyword.
2) If you are viewing the web through AOL, Google can become confused as to which country you are in. E.g. If you tell Adwords that you only want ads to be served to surfers in the UK and you access Google through AOL it is possible that you will not see your Ad, as Google thinks you are in America. The effect will vary depending on whether you use AOL's browser or access the web through AOL, but use Internet explorer.
I think the issue is quite likely to be your Daily Budget. I suspect that the budget you have chosen is less than the budget the AdWords program has suggested.
For more detail on this, and an easy method to check your daily budget in the *old* interface please see post #6 in this thread: [webmasterworld.com...]
To check your daily budget vs. suggested daily budget in the *new* interface, go to the campaign in question, click 'Edit Campaign Settings' and look underneath where your budget appears. If you see a message that says "Try $X.XX / day" then you know your actual budget is not sufficient to show your ad every time.
(An aside: let's say your actual budget is $1.00 and the suggested budget is $4.00. You can interpret this to mean that your ad is showing 25% of the time, spaced out over the 24 hour day.)
If you see "Budget is OK", well, then, your budget is OK - and you should be seeing your ad every time.
Gosh, I just barely stopped myself from saying "Hope that helps!". That was close. ;)