DW is merely obeying the rules of HTML and CSS and showing you, in advance,
the visual impact of your drag-and-drop workflow before it goes live. In
other words, it's doing you a favour before you put the site live and wonder
why it's broken :-)

Browsers read the code in your website so the more you understand about that
code, the less frustrations you'll encounter regardless of what design tools
you use.

For example:

>>Dreamweaver breaking CSS just by adding an "a" tag to an image

It sounds like you've got a finely-tuned, pixel-perfect sliced Photoshop
image which has a tolerance of less than a pixel before the page breaks.

By default browsers add a 1 pixel blue border to linked images to indicate
that they're linked. That's supposed to be helpful to end users but many
designers don't like the visual impact of the blue border. Sounds like this
single extra pixel is breaking your design which suggests to me that your
design needs more tolerance built in since you've got no idea of the device
(monitor, PDA etc) or browser viewport dimensions on which your site will be
viewed globally.

If you want to eliminate the blue border, add "a img { border: 0; }" to your
stylesheet.

Got a link to your current design?


--
Regards

John Waller