Web access to your host is platform independant. The MAC will access just fine.

There is not a requirement to match platforms to that of the webhost server. But you should be cognisant of the audience that you are trying to attract as this will generally be PC based and Win OS by default. This is to insure that your pages render correctly to these platform/browser types. I would not do all the design/tweaking on the MAC only to later find out that it does not look correct for others. You can Google for user stats and will find that 90+% are using PC Win machines and then you can look at the browser stats etc. No matter if we like it or not this is where it must look correct.

Normally, this is done with a PC/Win/Firefox as this is the most compliant base. Then it is also looked at in IE and this may require some browser specific alterations. Then we cross our fingers for Opera & Safari...