Sometimes I found it written as "WebPages" and sometimes it is "Web Pages" .. I'm confused should it be written as one word or two words ?!
Here is an Ngram chart of "web page" (blue line) versus "web pages" (red line) versus "webpage" (green line) versus "webpages" (yellow line) for the period 1980–2019:
As you can see, the two-word versions of these terms were strongly favored from roughly 1995 through about 2009 in the published documents included in the searchable Google Books database, but then they began to decline in frequency while the single-word forms continued to become more common. According to the data from Google Books, the two-word forms were still more common than their one-word counterparts as of 2019, but I expect that the trends favoring the one-word forms will continue and that webpage and webpages will be more common by 2030—and perhaps much sooner.
One reason for this change is that many English set phrases (such as "child care" and "check list") eventually compress from two words to one as they become commonplace in writing. Another reason is that trendsetting sources may favor the closed-up form owing to their early familiarity with the term.
In the case of "web page"/"webpage," I recall that the shift from the two-word spelling to the one-word spelling occurred in 2012 or 2013 at the two computer magazines where I was working at the time. A shift of that sort can have outsize influence because the term occurs more often in such specialized forums than in the outside world and because dictionaries often accord more weight to style choices that arise within a particular field or discipline than to style choices made by nonspecialists.
Merriam-Webster Online lists the term under the spelling web page (with Web page as an alternative spelling), although MW's most recent Collegiate Dictionary, the Eleventh Collegiate (2003) has no entry for the term at all. In contrast, the American Heritage Dictionary of the English Language Online lists webpage as the primary spelling (and Web page as an acceptable variant). In print, AHDEL has included an entry for webpage since the fourth edition (2000).
From what I have found from several sources on the Web, what you see on your screen in your Web browser is a Web page. It is considered the same thing as a book page. If you are referring to more than one Web page on a site, then the term is Web pages. Example: I found four Web pages on x site which provided a lot of information about bolt and nut sizes in both SAE and Metric sizes. The question now becomes should the word after Web be capitalized? After all, if a Web page is a book page, why shouldn't it be a web page? And here is the BIG question: Why do we capitalize web. i.e., Web? If you search for Web page, you will many results that include "web page" or "web pages." Same thing for the program you are using to view this document, it can be a Web browser or a web browser. I guess it just continues so show the the English language is the most complicated and hardest language to use.