I have designed an Ad in Illustrator which I need to export to insert into an email. When the client views on the Mac (I am working on PC), compression like artifacts are visible around the text (see below... it is mainly around the white text in the red background header box). I have tried:
I suppose you don't mean compression artifacts, but just pixels. I don't see any compression artifacts in your image.
Problem is: when exporting in pixel formats like JPEG, the edges of your letters won't be as smooth as in the Illustrator file. Never ever. There will always be pixels.
Does anybody know anything about saving as SVG? (scalable vector graphics). I saved an .ai file as .svg and opened it in Safari and it looked great, however Firefox would not open it. It seems SVG is a web-compatible vector format but is not yet supported by all browsers without plugins. Is this correct?
Saving as JPG / PNG
There's your problem. JPG is lossy. It will almost always leave visible compression artifacts; that's one reason why it's recommended more for photos than for graphics with regions of continuous color (text, backgrounds, etc.—i.e.; vector artwork). Historically, that was the rule-of-thumb criteria you used in deciding between JPEG and GIF. Nowadays GIF is passe'. Use PNG (PNG Not GIF). It's lossless and should suffice for most anything RGB.
Good luck on trying to get SVG content into email. ;-)