Mail bomb -
An orchestrated attempt to shut down a mail server by sending more messages than it can handle in a short period of time.

Makegoods -
Additional ad impressions which are negotiated in order to compensate an Advertiser for the shortfall of Online ads delivered versus the commitments outlined in the approved insertion order.

Mashup -
Merging of two or more pieces of content together to create a new piece of media.

Megabyte (MB) -
A multiple of the unit ‘byte’ for digital information, used to quantify computer memory or storage capacity equal to 1,000 kilobytes (or technically, 2^20 = 1,048,576 bytes). For the purposes of this document, this measure relates to creative file size. (See definition for Byte)

Megabyte (MB) -
A multiple of the unit ‘byte’ for digital information, used to quantify computer memory or storage capacity equal to 1,000 kilobytes (or technically, 2^20 = 1,048,576 bytes). For the purposes of this document, this measure relates to creative file size. (See definition for Byte)

Meme -
A piece of media, often a photo and copy together, that inspire copycat media which often go viral.

MicroBlogging -
Publishing very brief, spontaneous posts to a public Website, usually via a mobile device or wirelessly connected laptop (e.g. on Twitter).

Microsites -
Multi-page ads accessed via click-through from initial ad. User stays on the Publisher’s Website, but has access to more information from the Advertiser than a standard ad format allows.

Mid-roll  -
Form of Online Video ad placement where the ad is played during a break in the middle of the content Video. (See Pre-roll and Post-roll).

Minimum bid -
The lowest amount of money that a Pay Per Click Search Engine allows Advertisers to bid for a certain keyword. This amount is usually $0.01, $0.05, $0.10, $0.20, or $0.50.

Moderation -
The act of selecting media files for publication or not, based on rules and guidelines set out by the Publisher. Content can be pre-moderated, meaning they’re reviewed before they’re published, or post-moderated, meaning the media is published immediately after a user posts it, but a moderator may take the media down later if they find it violates their rules. Moderation can be done by people or by software.

Mouse-off -
The act of a user moving the cursor away (off) from the hot spot of an ad. Mouse-off by a user may trigger an event, such as collapsing an expanding panel or stopping any animation in progress.

Mouse-over -
The process by which a user places his/her mouse over a media object, without clicking. The mouse may need to remain still for a specified amount of time to initiate some actions like an expanding ad.

Multi-part MIME -
Also known (confusingly) as an “Email sniffer”, a Message format which includes both an HTML and a text-only version in the same message. Most (but not all) Email clients receiving messages in this format will automatically display the version the user’s system is set to show. Systems that can’t show HTML should show the text version instead.