Onload Functionality (VBScript)

I am having a difficult time working on some onload functionality for my website. I would like to set some defaults for the user each time they go to the website. I would like to set it so that:

1) The text size of the page is "medium"
2) The user's screen is full screen

And there are a couple more that are a bit more difficult. I am currently using <span> tags within my website so that I can hide/unhide certain areas based on the user selection. Apparently, not all computers unhide the spanned area and I know that you can set a default on the page so that the spanned area can be shown. I'm just not sure what the code is to do this.

If anyone could help with this, that would be great. Also, I would like a reference url so that I can explore this onload functionality some more. Thanks.