Question about how to access web pages

Although I now about the Symantec Norton Safeweb web page I was wondering if there is any other way of determining if a web page have any issues that one needs to worry about.

 

I had briefly communicated to a tech type person about a page that apparently had possible coding on it that was a type of mal-ware (delete all files they had mentioned) but was not sure how they were able to determine that that code was on that page especially since I would ASSUME that they would want to understand that code like that existed without actually going to that web address.

 

Thank you much,

Mumford68