Do you think that having my main keyword inside a <h1 style="font-size:16px"> a blackhat thing? Because I trully think <h1> is too big.. *shrugs*
No, that works fine. In fact you should also be using other "H" tags besides one. each give a slighty lower level of importance. BUT, use them properly, too many H1 tags on a page is obviously spam. Typically 1 or 2, then move to H2 ect. Follow the way a well written article works and you will be fine. You can also assign styles to the H tags so that they fit in like normal text, by using margin 0; That way you can use it in the middle of text like you would bold or other formatting tags.
no but probably better to style your h1 from your main css file. <style> h1 {font-size:16px;} </style>
Uhmm.. anyone had any problems with css cache? I mean if i change the css file a bit, some users still see the old colors for example, any hint?
If you have a large site this could be a potential problem for you users. Which browser are you having problems with?
I'm not sure this is true. The search engines try to figure importance the way a reader would. So if you look at a professional writen print article you can get the idea of the importance of the tags. H1 is a heading for the page and therefore gives the impression that these words are a short summary of or represent the entire page or at least until the next H1 H2 would be a subheading with in the main and therefore of slightly lower importance the an H1. However it's importance may reach several paragraphs untill the next H tag and so on. a bold or strong more or less says this word is more important than other words in this paragraph, there fore it is a weaker tag than the H tags.
Only for a little while. Their cashe will eventually refresh itself. Browsers are normally set by default to check when a page was last changed and update if the version in the cashe is different. I've never seen it hold more than a day before figuring out there was a change.