Is this a settings issue or a bigger problem? (Web design)

Mods, I posted this here but maybe it should be in the Web design - you can decide - apologies if Im wrong. Thank you.

Here goes:


My problem is I can enter .html code on a windows computer that i borrowed to test out my theory. I get my First Web Page banner the way is should look online in 5 mins. Yeah!!!

But......when I work on my MacBook Pro, no matter what I try (and Ive spent hours on something thats supposed to take 5 mins) it just wont look right when I go to view online

Im suspecting/hoping it has something to do with my Mac settings at this stage because it works on Windows for me. On my Mac I use Text Editor, save as a .html file and when I open it up as a browser page using Safari, all I see is the code entered not the Banner in its color. (when I say hoping, this mac is a refurb and I have visions of prolems arising).

Ive also tried saving the file as a .rtf file (for Text Editor), (saved as rich text I think it says - so not as a .html file). I then rename the file extension from .rtf to .html to enable me to open it in browser and heloooooo I see my banner........But also a lot of black text which isn't supposed to be there

Does anyone know what might be going wrong on the mac (settings perhaps), as I can do this fine on windows but not on the mac :-(

Thanks so much for any help anyone can give :-)

Im doing an online Web design Course, and so far the tutor has reverted me back to FAQs which I had done before that already, and all it suggested was to check and recheck the code, that its spaced correctly etc. Well its not something im doing wrong I believe as on a windows laptop it works fine.....so back to the tutor again :-) Meanwhile while waiting patiently for him to reply I thought Id ask here too!