google catched my one page on 4th and 10th of this month.

so google catched the page again in 6 days (10-4=6).

but google doesn't catch the page again for 10 days (today is 20th, 20-10=10) even the page has been modified for over 6 days.

it looks strange, how often does google check and catch a page normally?

are you talking about caching and archiving or just crawling?

last Cache of my homepage was March 30th. It seems it's almost random... I can have them every few days then go 3 weeks without them.

I am not sure if this thread belongs to "web hosting"

Google datacenters have a problem in these days.
They are testing new sandbox ALGO probably because too many new web-sites ranking temporarily like no sandbox, which is very unusual and even being thought as G broken something as it seen on webmasterworld.com discussions.
It is getting better, sometimes google screw the regular systems while testing new ALGOs but it exists for a while only. You do not need to worry, it should be start to get crawled properly.
Also check your backlinks, one of your strong backlink may be no longer linking to you and spiders are no longer visiting your web-site.

Cansomeone explain the difference? What does google do? I dont know much about SEO

The difference between what?

Thread moved to Web Design and Content since this is connected to SEO.

A good way to know if Google is caching your pages is to check your web statistics to find out when the page was last visited, there is an algorithm Google uses to spider pages and index the new results. I'll have to find it, this is just a dummy post to show someone at work how a forum works, sorry you're my guinea pig :)

Also Google tends to catch onto new content, hence if you are shown to add/modify content on your site (ie RSS etc.) then google will start to cache your site more oftern! Content is key and updating your site regularly will also help your google ranking as well!

never, i feel sad xD

Yup, the more often your site is updated, the more often google will spider it, and cache it.

A site that is updated every day, will probably get cached and spidered daily.

One that is only updated once in a blue moon, will probably get spidered and cached once in a blue moon. Google likes fresh content.