1. A method of protecting computers against web threats, the method comprising: embedding a script-based scan engine into a webpage requested by a client computer; receiving the webpage with the embedded script-based scan engine in the client computer; executing the script-based scan engine in the client computer; the script-based scan engine parsing the webpage to extract webpage content of the webpage; the script-based scan engine scanning the webpage content for web threats; and allowing the webpage to be rendered by a web browser in the client computer when the webpage is deemed safe by the script-based scan engine.