To be honest, this is more of a "how do web pages work?" question than a "how does KM work?" one -- but I haven't been able to solve the problem from that end, so I'm asking for help from this one.
I usually use Chrome (but sometimes Safari or Firefox or iCab when a website is recalcitrant). Usually, when I open a page the PageUp and PageDown keys work to scroll it -- but sometimes they don't. It's as if the page body isn't focused or attending to input, in some way; I can solve the problem by clicking within the page, after which the PageUp and PageDown keys do work. (The problem is not that the cursor is in a text box when the page opens; it isn't. The page isn't expecting text entry, it's just not responding to PageUp and PageDown.) I cannot find any pattern to which pages will respond and which won't, nor can I find any way to find out if one will respond other than by hitting a scroll key and seeing whether anything happens.
I'd like to find some way to automatically focus each page in whatever way it needs when it opens, so that I don't have to go through the "hit key -- scowl -- click in page body -- hit key again" sequence. But I can't just have KM automatically click somewhere in every new page that opens, because there might be a link at that location. (Ideally, I'd like to have this happen only if the cursor isn't in a text entry box, because some web pages do open that way, expecting immediate text input, in which case PageUp and PageDown should of course scroll the box, not the whole web page. This is why I'm not just rebinding the keys to trigger KM macros that will click in the page's vertical scroll bar.)
Searching the web for info on terms like "web page scroll" returns info that is too basic ("Press PageDown to scroll a web page down") and searching for ones like "web page body focus" returns info that's aimed at web developers and heavily reliant on javascript, which I'm not familiar with.
So if anyone can offer some suggestions or guidance, I would be very grateful!