"biggest glipe ever"
I shall reserve judgement until I know what a glipe is :-))))))
What is it that has gone? The whole page, the styling, the background or the logo?
Many CSS values are inherited - I'm not sure quite how to explain it - elements for which you haven't assigned a style can inherit the style that you assigned to an element higher up the page heirachy.
If you have a style sheet you should be putting all the formatting in there. You can specify other styles for different elements just by defining a new style in your style sheet then referencing it in your HTML. For instance suppose that you wanted some words to come out bigger than all the rest. (I'll put extra lines and spaces in as I'm not sure how it will appear on here). In your style sheet you define what you want it to look like:
That is defining the font size of all paragraphs with the class "bigtext" so in your HTML you reference it like this:
<p class="bigtext">All of this is going to come out extra large.</p>
If you miss out the "p" in front of ".bigtext"you don't restrict the style to a particular element. You could use the style like this:
<p>Most of this is normal but this bit is <span class="bigtext">very important</span> so I want it bigger than the rest</p>
There's a lot more to it than that of course and I'm not sure that it can really be explained in a few lines.
Read the W3Schools CSS tutorial, it will explain things far better than I can:
It also has try-it-yourself examples where you can change the code and see what the effect is.
Hope I haven't confused things even more.