We have several animated ads (each with 4 distinct frames) which will be submitted to online magazines. The magazines have fairly strict size limits for ads - 40k on one, 50k on another - so when I made it an animated GIF in Photoshop and exported it under the size limit, the image lost too much quality.
It seems like the best option will be to create an HTML5 ad. Assuming the magazine can accept that (they accept "tag code (all formats)", which sounds promising), this brings us to my question: if I give them a small HTML5 file which loads the images which I host externally, will that original size limit apply to the HTML5 file only, or to that file and to the externally-hosted images?
From what I've read, it looks like the main reason sites have file size limits is to prevent ads from making the main page load longer. So then I wonder if lazy loading of some sort would help matters (even just waiting until the rest of the document is loaded).
Then again, I don't know how they enforce size limits. If there enforcement is simple, they may not check what else it loads externally.
Finally, since this is a question which is about the interplay of magazine policy and web development, I wasn't sure if this is the best venue to ask it. So if StackOverflow is not the best place to ask this question, where should I ask it instead?
You should ask the publication for which you are interested in submitting a banner ad. Only they will truly understand their policies and the motivations behind them. Anyone else answering here would only be speculating with their answer.