... While Wal-Mart (WMT) might spend a meager 0.4% of sales on advertising, the sheer size of the company turns that tiny percentage into a significant budget. Wal-Mart's nominally higher-margin competitor, Target (TGT), spends closer to 2% of its sales on advertising, while Best Buy (BBY), as a specialty retailer, spends upwards of 3%. Finally, more upscale stores like Macy's typically spend on the order of 5%.Web sites are a high margin business. I think 10% is a pretty good baseline, with another 10% on top of that if you hope to grow.
The same kind of ratios can be seen in the car industry (automakers' generally spend 2.5% to 3.5% of revenue on marketing), liquor (5.5% to 7.5%), packaged goods (4% to 10%), and every other industry.
If you're in a services business, you might want to bump your starting point higher than 5%. For example, like most professional services firms, my company is more margin-oriented than volume-oriented, so fueling its growth requires that we spend a higher percentage of our revenues. Last year, our number was just over 8%, and I've seen companies spend upwards of 15% when warranted—especially young companies that need to invest to build their brand.
If you're launching a major new portal, you're going to see numbers far in excess of 100% for quite some time.