Hello. I am using Dreamweaver to create blasts. On the native file, the appearance is just as I want it, but when viewed in gmail, hotmail, aol, etc. there are often weird spacing, changes in fonts, and other changes to layout.
Usually this is not that big of a problem, but is there a particular reason why this occurs that someone can explain to me in layman's terms, so that I can explain it to a client when they realize the little differences to my layouts.
Email clients all use different rendering engines to display HTML and CSS, just like Firefox and Internet Explorer can display the same page differently.
Email clients like Outlook and Gmail are even more varied in the way they will show HTML emails. We've done a lot of research as to what is and is not supported - see http://www.campaignmonitor.com/css for that.
Use inline styles for stuff you need to show up in gmail. I wrote a kind of long and now a bit old blog entry that talks about why email is different. You may find it helpful.