Reserved tags have special meaning to the AdServer object. These are tags prefixed by ad. (ad-dot), and specify what size the ad is, what frame it should appear in, and how wide the ad border should be. You should not create new tags with the ad-dot prefix.
The Ad.Size.Tag reserved tag specifies what size of ad is eligible to be selected for this ad request. This tag is treated as a Required tag; that is, if you pass ad.size tag in an ad request, AdServer will only consider ads of that size for delivery. If Tag does not match one of the creative size tags as specified in Ad Manager, no ad is selected.
The following table shows the ads sizes and corresponding tags that are supported by default. Using Ad Manager, you can add or delete entries in this list as desired, as long as the Tag is specified correctly in the TagList.
| Tag | Description | Width | Height |
| Banner | Full Banner | 468 | 60 |
| NavBanner | Full Banner with Navigation Bar | 392 | 72 |
| Half | Half Banner | 234 | 60 |
| Square | Square Button | 125 | 125 |
| Button1 | Button #1 | 120 | 90 |
| Button2 | Button #2 | 120 | 60 |
| Micro | Micro Button | 88 | 31 |
| Vertical | Vertical Banner | 120 | 240 |
For example, if you put the tag “Ad.Size.Banner” in the TagList array and call the GetAd method, then the method will return only an ad that is 468 x 60 pixels.