In almost every form of marketing, the start of the piece is an advertisement for the rest of it. It has the primary job of selling the reader, viewer or visitor on continuing to read or view the piece or item.
Just as the headline of a newspaper article is there to sell the reader on reading that article.
In an ad this function is usually performed by the headline, any main imagery and possibly the opening line or lines of the copy.
In a TV or radio commercial it is the first few words spoken or printed on screen (as well as any other initial visuals on the TV screen).
In a website, the home page has this job. It is the ONLY job of a website home page – to get the visitor to click through to another page in the website.
The main graphic, main menu bar and heading on the home page as well as possibly the initial sentence of the copy, are there to sell the home page – to get the visitor to stick on the site long enough to see / read enough of the home page content to then be sold on clicking through to another page.
Effective marketing consists of a large number of discrete small steps.
Most marketing failures stem from unknowingly skipping steps. You then leave behind a large percentage of potential buyers.