Web pages are preprogrammed in two ways - one is a fixed size, no matter what - the other is a size that to an extent, adapts itself to the monitor (display mod actually). Fixed size ones are more common, I think - this site is an example.
To see more on the screen - which will redice sideways scrolling - you can adjust the resolution of your monitor - this will make everything on the screen smaller, so more will fit.
There is no facility for just adjusting web page sizes.
To see the current resolution and adjust it, right-click on a blank area of the desktop, and select Properties from the menu that appears.